B    3 


PROBLEMS  IN 
B  OTANY 

EIKENBERRY 


THE  LIST  PRICE 

> 
BOOK  IS.... f.~ 


GIFT   OF 
Agricultural  Educ.Div. 


MAIN  H»RARY-AGfriCULTUWE  DE 


BIOLOGY 
LIBRARY 


PROBLEMS  IN  BOTANY 


BY 

W.  L.  ^IKENBERRY 

ASSOCIATE   PKOFESSOB  OF   EDUCATION,  UNIVERSITY   OF   KANSAS 


GINN  AND  COMPANY 

BOSTON     •     NBW    YORK     •     CHICAGO     •     LONDON 
ATLANTA     •     DALLAS     •     COLUMBUS     •     SAN    FRANCISCO 


BIOLOGY 

R 
G 


-&jti 

MAIM  LIBRARY- AQRICULTURE  0EPT, 


COPYRIGHT,  1919,  BY 
W.  L.  EIKENBERRY 


ALL   BIGHTS   RESERVED 
419.12 


GINN  AND  COMPANY  •  PRO- 
PRIETORS •  BOSTON  •  U.S.A. 


PREFACE 

The  rapid  development  of  our  country  during  the  last  few 
years  has  brought  about  a  more  general  recognition  of  the  great 
importance  of  the  basic  industry  of  plant  production  and  of 
the  necessity  of  applying  the  scientific  method  to  this  industry. 
This  recognition  emphasizes  the  importance  of  the  study  of  the 
laws  of  plant  growth,  whether  under  the  name  of  botany  or  of 
agriculture. 

In  presenting  this  manual  it  is  the  intention  to  place  before 
high-school  pupils  a  series  of  problems  which  have  to  clo  with 
the  activities  of  plants  and  with  their  relations  to  human  interests. 

The  problem  method  of  presentation  has  been  used.  The 
experience  of  the  best  teachers  shows  that  the  interest  of  pupils 
is  better  maintained  when,  so  far  as  practicable,  each  labora- 
tory exercise  is  presented  as  a  definite  problem,  the  solution  of 
which  must  be  achieved  by  the  pupil  with  only  such  assistance 
as  will  enable  him  to  apprehend  the  problem  and  secure  the 
necessary  data.  Furthermore,  the  experiences  to  which  it  is  ex- 
pected that  the  pupils  will  apply  their  scientific  training  present 
themselves  as  discrete  problems,  and  it  is  therefore  highly  desir- 
able, educationally,  that  their  school  work  should  tend  to  pro- 
duce in  them  the  habit  of  solving  environmental  problems  in  a 
scientific  manner.  At  the  same  time  it  is  recognized  that  there 
are  some  topics  in  botany  as  in  any  other  science  that  do  not 
lend  themselves  readily  to  statement  in  the  form  of  problems. 
The  author  has  not  hesitated  to  depart  from  the  problem  method 
of  attack  in  the  case  of  individual  exercises  when  another  form 
appeared  desirable. 

The  manual  is  organized  about  the  activities  of  plants  rather 
than  about  their  structures.  The  leading  exercises  are  concerned 


with  problems  regarding  the  activities  of  plants  as  living  things. 
Questions  regarding  structure  naturally  arise  in  consequence  of 
the  study  of  function,  and  structures  are  studied  at  the  time 
when,  and  in  so  far  as,  they  contribute  to  an  understanding  of 
the  life  activities  of  plants.  The  primary  sequence  of  topics  is 
physiological  rather  than  anatomical. 

A  textbook  should  be  used  throughout  the  course,  and  refer- 
ences to  the  two  books  by  Bergen  and  Caldwell  are  provided. 
Discussions,  and  to  a  considerable  extent  the  names  of  structures, 
should  be  secured  from  the  textbook,  which  should  be  used  as 
a  reference  book  in  connection  with  the  laboratory  manual. 

The  author  has  sought  to  make  the  directions  to  pupils  as 
detailed  as  possible  without  destroying  opportunity  for  initiative 
on  the  part  of  the  pupil  or  solving  his  problems  for  him.  The 
study  or  experimentation  called  for  in  each  case  should  put  a 
pupil  in  possession  of  the  facts  upon  which  he  may  base  his  con- 
clusion. The  pupil  should  be  allowed  to  think  the  matter  through 
to  a  conclusion,  even  if  his  conclusions  are  sometimes  in  error. 

Printed  directions  do  not  make  a  teacher  unnecessary.  The 
teacher  should  require  dependence  upon  the  outlines-  for  all 
information  furnished  therein,  refusing  to  answer  questions  when 
the  guidance  sought  is  contained  in  the  printed  directions,  in 
order  that  his  time  may  be  reserved  for  the  more  important 
phases  of  teaching.  There  rests  with  the  teacher  the  responsi- 
bility for  calling  attention  to  errors  of  technique,  guiding  the 
thinking  of  those  who  need  assistance,  presiding  over  the  gen- 
eral discussions  in  which  the  class  compares  results  and  detects 
errors  of  fact  or  reasoning,  and  finally  checking  up  the  whole 
matter  by  examination  of  notes  and  drawings. 

A  record  of  all  laboratory  work  should  be  kept  by  each  pupil. 
Memoranda  should  be  made  during  the  progress  of  an  experi- 
ment, and  these  should  serve  as  the  basis  of  detailed  notes  which 
should  be  written  immediately  at  the  close  of  the  exercise.  The 
general  character  of  the  notes  is  discussed  in  connection  with 
the  directions  for  work  in  the  first  few  exercises.  However,  no 
printed  suggestions  to  pupils  will  secure  good  notes ;  the  respon- 
sibility rests  with  the  teacher.  Few  pupils  will  write  good  notes 

[iv] 


if  carelessly  written  ones  are  accepted  by  the  teacher,  but  most 
pupils  will  write  notes  which  come  up  to  the  standard  maintained 
by  the  teacher. 

Notes  and  drawings  should  be  collected,  examined,  and  graded 
weekly,  and  they  should  be  returned  to  the  pupils  promptly.  By 
this  means  errors  are  detected  at  once,  and  any  tendency  to 
postpone  note-writing  may  be  corrected. 

The  amount  of  drawing  which  is  called  for  in  this  manual  is 
not  great,  and  most  of  the  necessary  drawings  should  be  dia- 
grammatic. The  results  of  investigation  *of  the  psychology  of 
drawing  in  biological  study  have  shown1  that  there  is  little 
pedagogical  value  in  the  detailed  drawings  the  making  of  which 
formerly  occupied  such  a  large  place  in  biological  courses,  but 
that  diagrammatic  drawing  is  a  very  valuable  teaching  device. 
Diagrams  are  properly  employed  to  represent  the  pupil's  ideas 
regarding  the  relations  of  things  ;  detailed  drawing,  to  make  clear 
such  descriptive  facts  as  cannot  be  readily  represented  in  words. 

It  has  been  found  advantageous  to  take  the  class  out  of  the 
laboratory  and  into  the  field,  forest,  or  garden  for  many  exercises 
which  are  sometimes  worked  out  within  the  laboratory,  and  cer- 
tain other  exercises  ought,  if  possible,  to  constitute  home  proj- 
ects, as  indicated  in  connection  with  the  exercises.  It  is  always 
preferable  to  take  the  class  to  the  materials  in  their  natural 
surroundings  rather  than  to  bring  the  materials  into  the  labora- 
tory, if  the  former  course  is  practicable.  Each  outdoor  excursion 
made  by  the  class  should  be  directed  to  the  solution  of  a  definite 
problem  and  should  be  characterized  by  the  same  kind  of  serious 
work  as  characterizes  ordinary  laboratory  sessions.  Such  short 
excursions,  restricted  to  a  single  problem,  ar%  better  assimilated 
than  are  longer  and  more  or  less  confused  excursions.  They 
offer  the  further  advantage  of  avoiding  the  administrative  diffi- 
culties which  have  sometimes  put  field  work  in  disfavor. 

No  directions  are  given  for  all-day  field  trips.  Such  extended 
excursions  should  be  planned  whenever  possible,  but  local  con- 
ditions vary  so  widely  that  it  is  obviously  impossible  to  write 
directions  that  will  be  generally  applicable.  The  botanical  results 
1  F.  C.  Ayer,  Psychology  of  Drawing.  Warwick  and  York. 

[v] 


of  such  a  trip  will  depend  principally  upon  the  skill  and  the 
enthusiasm  of  the  teacher. 

It  is  not  probable  that  any  school  will  care  to  use  all  of  the 
exercises  presented  herewith.  In  some  cases  definite  alternatives 
have  been  suggested.  In  other  cases  traditional  exercises  have 
been  retained  because  under  some  circumstances  they  are  valu- 
able. Thus  the  exercises  involving  rather  careful  microscopic 
study  of  the  morphology  of  the  higher  plants  will  undoubtedly 
be  omitted  by  most  schools,  but  some  schools  may  find  them 
useful. 

Examination  of  the  apparatus  list  published  herewith  will 
indicate  that  expensive  equipment  is  not  essential,  and  it  will 
be  found  that  most  of  the  items  will  be  available  for  use  in 
other  science  courses  as  well.  The  principal  item  of  expense, 
microscopes,  may  be  eliminated  if  necessary,  but  every  school 
ought  to  possess  at  least  one  instrument.  In  many  cases  a  good 
microprojection  outfit  will  be  found  more  satisfactory  than  a  full 
equipment  of  microscopes.  While  extreme  economy  is  justified 
on  the  part  of  schools  with  very  limited  resources,  there  is  no 
point  at  which  the  proper  expenditure  of  funds  makes  for  effi- 
ciency and  economy  to  a  greater  extent  than  in  the  provision 
of  proper  laboratory  equipment.  Such  equipment  releases  the 
teacher  from  an  enormous  amount  of  detail  work  and  enables 
him  to  concentrate  his  attention  upon  the  needs  of  the  children 
instead  of  compelling  him  to  give  the  major  part  of  his  time  to 
the  mere  mechanics  of  instruction. 

The  author  wishes  to  express  his  deep  indebtedness  both  to 
the  literature  of  botany  and  of  botanical  education  and  to  his 
instructors,  colleagues,  and  pupils  who  together  have  made  this 
work  possible.  Particularly  does  he  gratefully  acknowledge  the 
instruction,  advice,  and  inspiration  received  from  Dr.  Otis  W. 
C  aid  well,  to  whose  encouragement  is  largely  due  both  the 
inception  and  the  completion  of  this  volume. 

W.  L.  E. 


[vi] 


CONTENTS 


I.  PLANTS  AND  WATER 

EXERCISE  PAGE 

1.  Plants  and  Water 1 

2.  Does  Water  evaporate  from  Shoots? 3 

3.  How  much  Water  may  evaporate  from  a  Plant? 4 

4.  What  hinders  the  Rapid  Evaporation  of  Water  and  Complete 

Drying  of  the  Leaf  ? 5 

5.  Structure  of  Epidermis 6 

6.  By  what  Route  does  Water  reach  the  Leaves  ? 7 

7.  Structure  of  Stems,  with  Special  Reference  to  Water  Conduction  8 

8.  Ornamental  Characteristics  of  Oak  Wood 10 

9.  Physical  Characteristics  of  Oak  Wood 12 

10.  General  Characteristics  of  Hard  Woods 13 

11.  Characteristics  of  Soft  Woods 14 

12.  Structure  of  a  Monocotyledonous  Stem 15 

13.  Water-Conducting  Tissues  of  a  Root 16 

14.  Has  a  Root  the  Ability  to  absorb  Water  and  to  assist  in  raising 

it  up  the  Stem  ? 17 

15.  Absorption  by  a  Root 18 

16.  Osmosis 19 

17.  Does  the  Form  and  Structure  of  the  Root  favor  Absorption?  .     .  20 

18.  Relation  of  Root  Hairs  to  Soil 21 

19.  Composition  of  Some  Plant  Substances 22 

II.  NUTRITION  OF  PLANTS 

20.  Production  of  Starch  in  Leaves    . 23 

21.  The  Chloroplasts 24 

22.  Is  Light  Necessary  for  Starch-Making  in  Leaves  ? 25 

23.  Is  Air  Necessary  for  Photosynthesis  ? 26 

24.  A  Waste  Product  of  Photosynthesis 27 

25.  How  is  Exposure  to  Light  favored  by  Leaf  Arrangement  ?  ...  28 

26.  How  do  Plants  without  Chlorophyll  secure  their  Food  ?   A  Parasite 

as  an  Example 30 

27.  A  Saprophyte;  Mold  as  an  Example 31 

[vii] 


EXERCISE  PAGE 

28.  What  Use  may  the  Plant  make  of  Food  Materials,  such  as  Starch?  32 

29.  How  may  Insoluble  Foods,  as  Starch,  be  moved  from  Place  to 

Place  in  the  Plant? 33 

30.  Digestion  of  Starch 34 

31.  What  Provisions  are  made  Annually  for  Next  Year's  Growth  of 

Branches  ?   Food  Storage 36 

32.  Preparation  for  New  Growth  in  the  Structure  of  the  Bud   ...  37 

III.  PROVISION  FOR  GROWTH 

33.  The  Opening  of  a  Bud 39 

34.  The  History  of  the  Growth  of  a  Branch 40 

35.  Some  Examples  of  Extensive  Storage  of  Foods 42 

36.  The  Use  made  of  Stored  Food 44 

37.  How  does  the  Amount  of  Available  Stored  Food  affect  Growth  ?  .  45 

38.  Field  Study  of  Food  Storage 47 

IV.  REPRODUCTION  AND  PROPAGATION 

39.  Vegetative  Reproduction  by  Stolons  and  Runners 48 

40.  Reproduction  from  Leaves 49 

41.  Reproduction  from  Roots 50 

42.  Propagation  by  Roots 51 

43.  Propagation  by  Softwood  Cuttings 52 

44.  Cleft  Grafting 53 

45.  Budding 55 

46.  The  Parts  of  a  Flower 57 

47.  How  are  Seeds  and  Fruit  formed  from  the  Pistil  ? 59 

48.  How  is  Pollen  carried  from  Stamen  to  Stigma  ? 60 

49.  Prevention  of  Self-pollination  by  Dichogamy 62 

50.  Prevention  of  Loss  of  Pollen 63 

51.  Can  Pollen  be  distributed  by  Wind  ? 64 

V.  SEED  DISPERSAL 

52.  Advantages  from  Dispersal  of  Seeds 65 

53.  What  Advantages  are  possessed  by  Plants  having  Winged  Seeds 

or  Fruits  ? 66 

54.  What  Advantages  are  possessed  by  Plants  having  Plumed  Seeds 

or  Fruits  ? 68 

55.  What  Advantage  in  possessing  Burs  or  Stickers  ? 69 

56.  Dispersal  of  Seeds  of  Fleshy  Fruits  . 71 


VI.  SEEDS  AND  SEEDLINGS 

EXERCISE  PAGE 

57.  Production  of  a  Plant  from  a  Seed 72 

58.  Structure  of  a  Seed 73 

59.  Comparison  of  Seeds  and  Seedlings 74 

60.  The  Cotyledons •  .     .  75 

61.  A  Monocotyledonous  Seed 76 

VII.  RELATION  TO  ENVIRONMENT 

62.  What  is  the  Effect  of  Different  Temperatures  on  Germination  ?  77 

63.  What  is  the  Effect  of  Gravity  on  the  Growth  of  Root  and  Stem  ?  79 

64.  How  do  Stems  and  Leaves  react  to  Light? 80 

65.  Response  to  Touch 81 

66.  Response  of  Tendrils 82 

67.  Respiration •.     .     .  83 

68.  How  much  Force  does  the  Wind  exert  against  a  Tree  ?      .     .     .  84 

69.  Does  the  Bark  assist  in  Strengthening  the  Stem  ? 85 

70.  Tensile  Strength  of  Bark 86 

71.  Competition  between  Branches,  and  Self-pruning 87 

72.  In  what  Manner  are  Wounds  in  Trees  Healed? 89 

73.  What  Precautions  are  Necessary  in  Transplanting  Young  Plants  ?  91 

74.  Transplanting  Trees  or  Shrubs  . 92 

VIII.  RELATION  OF  SIMPLE  PLANTS  TO  MAN'S  LIFE 
AND  INDUSTRIES 

75.  What  are  the  Size,  Shape,  Motion,  and  General  Appearance  of 

Bacteria? 93 

76.  To  study  the  Growth  and  Distribution  of  Bacteria 95 

77.  Physiology  of  Yeast      . 98 

78.  Structure  of  Yeast 100 

79.  Preparation  of  Mold  Cultures 101 

80.  Bread  Mold 102 

81.  Detection  of  Molds  in  Air  and  in  Other  Places 103 

82.  Blue  Mold,  or  Blue  Mildew 104 

83.  Yellow  Mold  or  Yellow  Mildew 105 

84.  Lilac  Mildew  —  a  Parasitic  Fungus 106 

85.  Wheat  Rust  — a  Destructive  Parasite 107 

86.  Fungi  which  cause  Plant  Disease .'     .     .  109 

87.  A  Mushroom 110 

88    Wood-rotting  Fungi Ill 

89.  Classification  of  Fungi 112 

[ix] 


to  be  used,  and  also  of  the  manual  itself,  which  provides  for  the 
essential  first-hand  experience  with  plants.  Such  experience  is 
of  the  highest  importance.  The  manual  represents  a  distinct  ad- 
vance in  botanical  instruction  in  secondary  schools  because  of 
the  way  in  which  it  insures  abundant  experience  with  plants.  It 
provides  outlines  by  means  of  which  the  laboratory  presenta- 
tion of  botanical  study,  as  well  as  the  text  presentation,  may 
be  in  accord  with  the  most  recently  defined  ideals  for  science 
work  in  secondary  education. 

Textbooks  and  laboratory  manuals  of  botany  are  of  two 
types,  —  office  made  or  made  through  experience.  This  manual, 
like  the  texts  with  which  it  is  designed  to  serve,  is  the  result 
of  many  years  of  successful  experimentation  in  secondary-school 
teaching.  This  method  of  developing  an  outline  of  study  seems 
to  be  the  only  one  really  worthy  of  science.  If  trial,  correction, 
retrial,  selection,  and  elimination  —  that  is,  the  experimental 
basis  —  are  essential  in  the  development  of  our  knowledge  of 
science,  surely  the  same  experimental  basis  is  essential  to  the 
development  of  courses  of  science  study. 

Since  this  manual  is  the  result  of  such  careful  experience,  it 
should  prove  of  great  value  to  young  people  who  have  the 
opportunity  of  using  it.  QTig  w_ 


[xii] 


PROBLEMS  IN  BOTANY 


EXERCISE  1 
PLANTS  AND  WATER 

Materials.  Several  potted  plants  of  coleus  or  anything  else  that  is 
rather  delicate.  The  plants  used  should  be  as  nearly  alike  in  size 
and  general  appearance  as  possible. 

Directions  for  work.  Place  all  of  the  plants  in  a  warm,  dry, 
light  place.  Water  one  half  of  them  freely,  but  do  not  water 
the  remainder  during  the  experiment. 

Examine  the  plants  daily.  After  several  days,  or  possibly 
within  one  day,  differences  in  the  appearance  and  behavior  of 
the  two  lots  of  plants  may  be  seen. 

State  on  paper  what  differences  between  the  plants  you  see. 
What  explanation  can  you  offer  for  the  change  which  has 
occurred  in  one  lot  of  plants  ?  What  reasons  have  you  for 
this  explanation  ?  Is  there  any  way  in  which  you  can  test  the 
accuracy  of  your  explanation  ? 

Make  a  list  of  all  the  questions  which  come  into  your  mind 
as  a  result  of  this  experiment,  and  preserve  this  list  for  further 
use  as  you  continue  the  study  of  the  relation  of  water  to  plants. 

Notes.  It  is  usually  desirable  to  make  a  written  record  of 
any  laboratory  study.  Such  a  record  may  be  brief;  it  must  be 
accurate.  It  should  be  written  in  good  English  and  with  as 
much  care  as  a  theme  in  the  English  class.  If  the  exercise  is 
an  experiment,  as  this  one  is,  there  will  be  three  parts  to  the 
composition,  as  suggested  below,  and  each  of  the  parts  will 
commonly  appear  as  a  separate  paragraph.  Write  notes  on  this 
exercise  according  to  the  following  suggestions : 


EXERCISE  1  (Continued) 

1.  Give  an  account  of  what  was  done,  either  by  the  instructor 
or  by  you,  in  carrying  out  the  experiment.    Be  careful  to  omit 
nothing  that   might  in   any    way  influence    the  result   of   the 
experiment.    Make  it  clear  enough  so  that  an  absent  classmate 
would  be  able  to  perform  the  experiment  at  a  later  time  with 
no  other  guide,  than  your  notes.    Illustrate  by  sketches  if  it 
.will  assist  yo;a. , 

2.  Whatf  results  •  did  you  observe?    State  the  facts  observed, 
witriout  your  opin-ions.    Make  the  statement  as  definite  as  pos- 
sible.   When  the  results   can  be   expressed   in  figures   (as  in 
Exercise  3)  these  figures  should  be  given. 

3.  State  your  conclusions.    What  have  you  learned  from  the 
experiment?    What  is  your  explanation  of  the  meaning  of  the 
observed  results?    What  are  the  reasons  which  convince  you 
that  your  explanation  is  correct?     What  further  question  or 
what  additional  experiment  does  it  suggest? 


[2] 


EXERCISE  2 
DOES  WATER  EVAPORATE  FROM  SHOOTS? 

Materials.  Geranium  plant ;  two  six-ounce,  wide-mouthed  bottles  ; 
cork  stopper  or  wad  of  cotton ;  support  with  clamp. 

Directions  for  work.  While  the  geranium  is  suggested  for  this 
study,  almost  any  common  plant  will  answer  if  the  leaves  are 
small  enough  to  be  treated  as  directed  below.  Trees  or  shrubs 
out  of  doors  may  be  used. 

Insert  the  end  of  a  leafy 
shoot  into  one  of  the  bottles 
and  support  the  bottle  in  such 
manner  that  the  shoot  will  be 
in  approximately  natural  posi- 
tion. Select  a  cork  stopper 
which  fits  the  bottle  and  punch 
a  hole  through  it  large  enough 
to  accommodate  the  stem 
which  has  been  inserted  into 
the  bottle.  Split  the  stopper 
through  the  center  of  the  hole 
and  place  the  two  halves  in 
the  neck  of  the  bottle  with  the 
stem  in  the  hole.  (See  Cald- 
well  and  Eikenberry,  "  Elements  of  General  Science,"  Fig.  62.) 
If  a  large  stopper  is  not  at  hand,  the  neck  of  the  bottle  may 
be  plugged  with  cotton.  For  purposes  of  comparison,  support 
a  similar  bottle,  stoppered  but  with  no  leaves  in  it,  near  the 
first.  If  a  potted  plant  is  used,  place  it  in  a  light  place. 

Examine  at  intervals  during  the  next  hour  in  order  to  de- 
termine whether  there  is  evidence  that  water  is  given  off. 

What  are  the  facts  that  you  observe  ?  What  are  your  con- 
clusions regarding  the  loss  of  water  from  shoots? 

Review  the  directions  for  writing  notes  as  given  in  connec- 
tion with  the  previous  exercise,  and  write  notes  on  this  exercise. 

Reference 

BERGEN  and  CALDWELL.    Practical  Botany,  p.  18. 

[3] 


EXERCISE  3 
HOW  MUCH  WATER  MAY  EVAPORATE  FROM  A  PLANT? 

Materials.  A  potted  plant ;  sheet  of  dentist's  rubber  large  enough 
to  inclose  the  pot;  balance  and  weights. 

Directions  for  work.  In  order  to  determine  the  answer  to  the 
question  above,  proceed  as  follows: 

Water  the  pot  thoroughly.  Wrap  it  in  the  sheet  rubber  and 
tie  the  rubber  about  the  stem  so  that  water  is  prevented  from 
evaporating  from  the  soil  or  pot. 

Weigh  the  plant  at  hourly  intervals  during  the  daytime  for 
at  least  two  days.  The  pupils  may  take  turns  in  weighing 
throughout  the  day,  the  weights  being  recorded  on  the  black- 
board for  the  benefit  of  all. 

Tabulate  the  results  as  follows: 


DATE 

HOUK 

WEIGHT 

HOURLY  Loss 

TOTAL  WATEK 

EVAl'OKATED 

Reference 

BERGKN  and  CALDWELL.    Practical  Botany,  p.  18. 


[4] 


EXERCISE  4 

•      WHAT  HINDERS  THE  RAPID  EVAPORATION  OF  WATER 
AND  COMPLETE  DRYING  OF  THE  LEAF? 

Materials.  Leaves  of  lily,  amaryllis,  hyacinth,  iris,  or  similar 
plant;  sharp  knife. 

Directions  for  work.  With  the  knife  make  a  slight  cut  ob- 
liquely through  the  surface  layer  of  the  leaf.  Catch  hold  of  the 
surface  layer  at  the  edge  of  the  cut  with  the  thumb  and  the 
knife  blade,  and  peel  off  some  of  it.  This  is  usually  more 
easily  accomplished  on  the  lower  side  of  the  leaf.  The  thin 
layer  removed  is  the  epidermis. 

Remove  the  epidermis  from  as  much  as  a  half -inch  or  quarter- 
inch  square  of  leaf  and  allow  a  piece  of  leaf  with  epidermis 
removed  to  lie  on  the  desk  alongside  a  piece  with  epidermis 
uninjured  for  as  long  as  an  hour  if  possible.  Note  the  changes 
that  take  place  in  either  piece. 

While  waiting  for  the  progress  of  the  above  experiment, 
examine  the  epidermis  carefully.  Note  especially  its  thickness, 
color,  and  degree  of  transparency.  Examine  also  the  material 
which  occupies  the  interior  of  the  leaf,  noting  its  color,  thick- 
ness, and  texture.  Where  does  most  of  the  moisture  in  the 
leaf  appear  to  be  found? 

Compare  the  two  pieces  of  leaf  which  have  been  exposed  on 
the  desk  as  directed  above.  What  changes  have  taken  place  ? 
What  are  you  able  to  conclude  regarding  the  value  of  the 
epidermis  to  the  leaf? 

Write  notes  as  in  the  preceding  exercises. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  13,  14. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  34,  35. 


[5] 


EXERCISE  5 
STRUCTURE  OF  EPIDERMIS 

Materials.  Compound  microscope;  glass  object  slides  and  cover 
slips ;  leaf  epidermis. 

Directions  for  work.  Mount  a  small  piece  of  epidermis  in 
water  on  a  slide  and  cover  with  a  cover  slip.  (Secure  detailed 
directions  for  using  microscope  from  the  teacher.)  Examine 
with  low  and  high  power. 

Note  that  the  epidermis  is  made  up  mostly  of  rectangular 
units,  called  cells,  as  a  pavement  is  composed  of  bricks.  Certain 
o'f  the  cells  are  bean  shaped  and  are  found  in  pairs. 

Do  you  find  spaces  between  cells  forming  openings  through 
the  epidermis  ?  If  so,  describe  and  locate  them  clearly  enough 
to  enable  any  one  else  to  find  them  readily  by  the  aid  of  your 
notes.  Such  openings  are  called  stomata  (singular  stoma). 

How  do  these  openings  assist  in  explaining  the  loss  of  water 
by  evaporation? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  13,  14. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  34~36. 


[6] 


EXERCISE  6 
BY  WHAT  ROUTE  DOES  WATER  REACH  THE  LEAVES? 

Materials.  Leafy  branches  of  tree  or  shrub,  preferably  at  least 
one-half  inch  thick  at  base ;  soft  leafy  stems,  such  as  geranium, 
coleus,  celery,  or  almost  any  common  weed  or  herbaceous  flowering 
plant,  but  semitransparent  stems,  as  yellow  coleus,  are  best;  eosin 
or  red  ink. 

Directions  for  work.  Color  some  water  with  eosin  or  with 
red  ink.  Stand  freshly  cut  stems  with  lower  ends  in  the 
colored  water.  Place  the  experiment  in  a  sunny  place  for 
later  examination. 

1.  Woody  stems.    When  the  branches  have  been  standing  in 
the  colored  water  for  some  hours,  remove  them  from  the  solu- 
tion and  cut  sections  at  various  heights  along  the  stems.    Also 
split  the  pieces  lengthwise.    Trace  the  path  of  the  water  into 
the  branches  and,  if  possible,  to  the  leaves. 

Does  the  water  travel  in  the  pith,  the  wood,  or  the  bark  ? 
(See  textbook  for  definition  of  terms.)  What  can  you  learn 
about  the  distribution  of  water  throughout  the  leaves? 

2.  Herbaceous  stems.  From  twenty  minutes  to  an  hour  is  suf- 
ficient to  secure  results  with  such  stems  as  geranium  or  coleus. 

Section  and  examine  in  the  same  way  as  directed  for  woody 
stems.  Note  carefully  the  path  of  the  water. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  p.  11. 

BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  12,  13. 


[7] 


EXERCISE  7 

STRUCTURE  OF  STEMS,  WITH  SPECIAL  REFERENCE  TO 
WATER  CONDUCTION 

Materials.  Cross  sections  of  oak  branch  or  trunk  three  to  six 
inches  in  diameter ;  microscope  slides  with  sections  of  woody  stems 
and  herbaceous  stems. 

The  oak  sections  may  be  prepared  by  cutting  a  seasoned  oak 
branch  into  sections  about  one  inch  long  and  carefully  smoothing 
one  cut  surface  with  fine  sandpaper.  If  red  oak  is  used,  the  distinc- 
tion between  sapwood  and  heartwood  will  be  prominent.  The  sections 
may  be  retained  as  permanent  laboratory  apparatus  if  the  surfaces 
are  oiled  and  varnished. 

Directions  for  work.  1.  Examine  the  smoothed  surface  for 
water-conducting  tubes  appearing  in  cross  section  as  round  pores, 
just  visible  to  the  naked  eye  but  easily  seen  with  a  lens.  These 
pores  may  be  filled  with  dust  due  to  the  sandpapering.  The 
dust  may  be  removed  by  a  vacuum  cleaner,  or  a  part  of  the 
surface  may  be  smoothed  with  a  sharp  knife. 

How  does  the  location  of  the  pores  correspond  with  the  loca- 
tion of  the  water-conducting  region  discovered  in  the  preced- 
ing exercise  ?  Are  the  pores  scattered  at  random  through  the 
branch,  or  are  they  arranged  in  any  definite  way  ?  If  a  new 
layer  of  wood  grows  each  year,  what  relation  do  the  pores 
appear  to  have  to  this  annual  growth? 

Count  the  annual  layers  to  determine  the  age  of  the  tree. 
About  how  many  years  did  it  take  this  tree  to  increase  one 
inch  in  diameter  ? 

Make  a  diagram  of  the  cross  section  showing  location  of  pith, 
wood,  bark,  annual  layers,  medullary  rays,  heartwood,  and 
sapwood.  (See  textbook  for  definitions  and  for  assistance  in 
identifying  structures.) 

2.  With  the  compound  microscope  examine  thin  sections  of 
woody  twigs  two  or  three  years  old.  Identify  wood,  pith,  bark, 
annual  layers,  medullary  rays.  Represent  the  cross  section  dia- 
grammatically  and  label  the  structures  named  above.  Draw  a 
few  cells  from  the  wood,  including  at  least  one  large  pore. 

[8] 


EXERCISE  7  (Continued) 

Study  a  cross  section  of  a  coleus  or  other  herbaceous  stem 
and  find  the  water-conducting  tissue,  comparing  thin  sections 
with  stems  colored  as  in  Exercise  6.  When  you  have  accurately 
located  the  water-conducting  tissue,  study  its  structure  and 
draw  a  few  cells.  Do  they  resemble  any  of  the  cells  found  in 
the  woody  stems  ?  Is  the  water  conducted  in  the  wood  or  in 
the  pith? 

By  the  aid  of  your  textbook  find  the  pith,  fibrovascular 
bundles,  cortex,  epidermis.  Make  a  diagram  of  the  cross  section 
and  label  the  parts. 

The  wood  and  bark  of  older  stems  result  mainly  from  the 
growth  of  the  fibrovascular  bundles,  but  the  details  cannot  be 
followed  out  in  elementary  laboratory  work.  However,  the 
wood  part  of  the  bundle  (inner  part)  and  the  bark  part  (outer 
part)  may  be  distinguished  along  with  the  line  of  growing  cells, 
cambium,  which  lies  between  wood  and  bark. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  11-13,  44-53. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  11,  12,  62-68. 


[91 


EXERCISE  8 


ORNAMENTAL  CHARACTERISTICS  OF  OAK  WOOD 

Materials.  Cross  sections  of  an  oak  log  about  three  inches  in 
diameter,  as  used  in  Exercise  7  ;  a  section  of  a  seasoned  white  oak  log 
about  four  or  five  inches  in  diameter  and  six  inches  long  or  longer. 

Directions  for  work.  With  the  cross  sections  of  wood  in 
your  hands  identify  pith,  heartwood,  sapwood,  annual  layers, 
medullary  rays,  inner  bark,  and  outer  bark.  Note  whether 
the  specimen  represents  a  slow-growing  or  a  rapid-growing 

species.    Is  it  ring-porous  or 
diffuse-porous  ? 

Cut  a  section  five  or  six 
inches  long  from  the  larger 
log  and  saw  lengthwise  into 
boards  about  one-half  inch  in 
thickness.  Smooth  both  sides 
of  these  boards  with  a  plane 
and  sandpaper.  The  sawing 
and  rough  planing  should  be 
done  on  the  power  saw  and 
planer  in  the  school  shops 
if  the  school  possesses  such 
machinery. 

One  or  two  of  these  boards  will  show  surfaces  that  are 
nearly  parallel  with  the  medullary  rays.  These  correspond  with 
"  quarter-sawed  oak."  Find  these  boards  and  mark  them.  In 
the  remainder  of  the  boards  the  surfaces  are  tangential  to  the 
annual  layers.  They  may  be  called  "  plain-sawed  "  boards. 

Identify  sapwood,  heartwood,  medullary  rays,  and  wood 
pores  on  the  planed  surfaces  of  each  board.  Describe  each 
of  these  clearly  enough  for  purposes  of  identification  by  a 
beginner. 

Determine  the  relation  of  the  structural  elements  of  the  wood 
mentioned  above  to  the  appearance  of  the  wood  in  finished 
furniture  in  the  following  manner.  Treat  one  plain-sawed  sur- 
face with  linseed  oil,  a  second  with  a  dark  wood-filler,  and  a 

[10] 


EXERCISE  8  (Continued) 

third  with  a  brown  stain,  following  manufacturers'  directions  in 
each  case.  After  they  have  dried,  study  the  boards  to  determine 
how  the  summer  wood,  spring  wood,  sapwood,  and  medullary 
rays  react  to  the  finishes.  Does  sapwood  or  heartwood  finish 
better?  To  which  of  the  structural  elements  of  the  wood  is 
the  "  figure  "  of  the  wood  principally  due  ? 

Repeat  the  above  with  the  quartered  surfaces  and  determine 
the  same  facts. 

Compare  with  oak  furniture,  floors,  doors,  etc.  and  classify 
these  as  to  excellence  of  materials  and  finish. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  44-52,  391-393. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  109,  110. 


EXERCISE  9 
PHYSICAL  CHARACTERISTICS  OF  OAK  WOOD 

Materials.  Sticks  of  seasoned  white  oak  one  inch  square  and  two 
feet  long;  other  sticks  of  the  same  wood  but  only  one-half  inch 
square ;  several  rectangular  blocks  of  oak ;  several  small  boards  of 
green  oak,  which  may  be  sawed  from  a  freshly  cut  log  as  directed 
in  Exercise  8.  Some  boards  must  be  radial  and  others  tangential. 

Directions  for  work.  What  is  the  weight  of  oak  wood  ?  De- 
termine this  by  measuring  several  of  the  rectangular  blocks, 
weighing  them,  and  calculating  the  weight  per  cubic  foot. 
Average  results  from  the  several  blocks. 

What  is  the  strength  of  oak  wood  ?  Support  a  stick  of  oak 
at  two  points,  as  by  laying  it  across  two  bricks.  Measure  the 
distance  between  the  places  of  support.  Note  the  approximate 
amount  of  bending  under  different  strains,  as  when  persons  of 
known  weight  stand  on  a  stick  at  a  point  midway  between  the 
supports.  If  the  stick  is  broken,  note  the  weight  which  breaks  it. 

What  is  the  difference,  if  any,  between  plain  and  quartered 
oak  as  to  amount  of  warping  ?  Select  several  of  the  green  boards 
for  a  drying  test,  making  sure  that  in  the  lot  there  is  at  least 
one  radial  (quartered)  board  and  one  tangential  (plain)  board. 
Expose  them  to  the  air  and  heat,  but  see  that  all  boards  have  as 
nearly  as  possible  the  same  exposure.  Support  in  such  manner 
that  the  air  has  access  to  both  sides  of  each  board,  and  turn  them 
daily  in  order  that  both  sides  may  be  equally  exposed  to  drying. 

Which  boards  warp  the  most  ?  Which  the  least  ?  Which  side 
of  a  plain-sawed  board  becomes  concave  ? 

In  your  notes  sum  up  what  you  have  learned  about  the  weight, 
strength,  and  seasoning  of  oak  wood. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  393-395. 

BERGEN  and  CALDWELL.  Introduction  to  Botany,  pp.  62-67, 107,  108. 

"Mechanical  Properties  of  Woods  grown  in  the  United  States,"  Cir- 
cular No.  213,  Forest  Service,  U.  S.  Dept.  Agr. 

CLINE  and  HEIM.  "Tests  of  Structural  Timbers,"  Bulletin  No.  108, 
Forest  Service,  U.  S.  Dept.  Agr. 

[12] 


EXERCISE  10 
GENERAL  CHARACTERISTICS  OF  HARD  WOODS 

Materials.  Blocks,  boards,  or  small  logs  of  a  large  variety  of  hard 
woods ;  wood  sections. 

Directions  for  work.  Study  the  specimens  of  woods  available, 
noting  the  characteristics  with  sufficient  fullness  to  enable  any- 
one to  discriminate  between  them  by  the  use  of  your  notes  only. 
Note  especially,  color,  apparent  weight,  medullary  rays,  thick- 
ness of  annual  layers,  ring-  or  diffuse-porous,  size  of  pores,  appear- 
ance of  finished  surfaces,  and  any  individual  peculiarities. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  chap.  xxii. 

BERGEN  and  CALDWELL.  Introduction  to  Botany,  pp.  62-68,  chap.  viii. 

SUDWORTH  and  MELL.  "  Circassian  Walnut,"  Circular  No.  212,  Forest 

Service,  U.  S.  Dept.  Agr. 

MAXWELL.  "  Uses  of  Commercial  Woods  of  the  United  States  :  Beech, 
Birches,  and  Maples,"  Bulletin  No.  12,  U.  S.  Dept.  Agr. 


[13] 


EXERCISE  11 
CHARACTERISTICS  OF  SOFT  WOODS 

Materials.  Boards,  blocks,  and  sections  of  gymnosperm  woods, 
such  as  pine,  cedar,  hemlock,  redwood,  fir,  spruce,  and  cypress. 

Directions  for  work.  Study  as  directed  in  Exercise  10.  In 
addition,  note  character  of  wood  in  relation  to  presence  of  pores. 
If  possible,  examine  thin  cross  sections  with  a  microscope.  Dis- 
cuss the  differences  between  the  wood  of  angiosperms  and  that 
of  gymnosperms  (so-called  hard  woods  and  soft  woods). 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  chap.  xxii. 

BERGEN  and  CALDWELL.    Introduction  to  Botany,  chap.  viii. 

HALL  and  MAXWELL.    "  Uses  of  Commercial  Woods  of  the  United 

States  :  I.  Cedars,  Cypresses,  and  Sequoias,"  Bulletin  No.  95,  Forest 

Service,  U.  S.  Dept.  Agr. 
HALL  and  MAXWELL.    "Uses  of  Commercial  Woods  of  the  United 

States  :  II.  Pines,"  Bulletin  No.  99,  Forest  Service,  U.  S.  Dept.  Agr. 
CLINE  and  KNAPP.    "Properties  and  Uses  of  Douglas  Fir,"  Bulletin 

No.  88,  Forest  Service,  U.  S.  Dept.  Agr. 


EXERCISE  12 

STRUCTURE  OF  A  MONOCOTYLEDONOUS  STEM 
Materials.    Stems  of  corn  ;  pieces  of  palm  stem. 

Directions  for  work.  Not  all  stems  are  like  those  studied. 
The  stems  studied  in  the  preceding  exercise  belong  to  the 
dicotyledonous  group ;  the  corn  and  palm  are  representative 
of  the  monocotyledons.  (See  illustrations  and  discussions  in 
"  Practical  Botany,"  pp.  335-350.) 

Examine  the  cross  section  of  a  corn  stem,  noting  the  distri- 
bution of  the  fibrovascular  bundles.  Also  cut  the  stem  length- 
wise and  trace  some  of  the  bundles. 

By  the  use  of  colored  water  follow  the  path  of  the  water 
through  the  stem,  as  in  Exercise  6. 

Compare  the  corn  stem  with  the  palm.  Make  a  diagram 
showing  how  the  bundles  are  arranged. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  53,  54,  335-350. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  68. 


[15] 


EXERCISE  13 
WATER-CONDUCTING  TISSUES  OF  A  ROOT 

Materials.  Piece  of  root  from  a  tree.  Koot  should  be  about  an 
inch  in  diameter. 

Directions  for  work.  Cut  cross  sections  of  the  root.  Compare 
its  structure  with  that  of  the  stem,  which  it  closely  resembles. 
Note  the  large  water-conducting  pores. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  6-10,  24,  25. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  9,  10,  20-25. 


[16] 


EXERCISE  14 

HAS  A  ROOT  THE  ABILITY  TO  ABSORB  WATER  AND  TO 
ASSIST  IN  RAISING  IT  UP  THE  STEM? 

Materials.  Vigorous  plant  with  a  single  firm  stem  about  one-fourth 
inch  in  diameter;  glass  tube   about  one-fourth  inch  in  diameter 
and  ten  to  twelve  inches  in  length,  preferably  with  bore  of  small 
diameter ;  rubber  tubing ;  copper  wire  about  No.  18 ; 
pliers.  [i 

Either  a  potted  plant  or  one  growing  in  the  soil 
out  of  doors  may  be  used,  but  it  will  be  difficult, 
if  not  impossible,  to  secure  results  with  plants  that 
are  near  the  end  of  their  season's  growth.  A  potted 
bryophyllum  plant  has  been  found  very  satisfactory. 

This  exercise  and  the  two  following  may  be  set  up 
at  the  same  time  by  different  members  of  the  class. 

Directions  for  work.    Cut  the  stem  as  close*  to 
the  root  as'  possible.    To  the  stub  remaining  in 
connection  with  the  root  attach  the  glass  tube, 
using  a  short  piece  of  rubber  tubing  as  connec- 
tion and  bringing  the  glass  tube  and  stem  into 
contact  within  the  rubber  tube.    Make   sure   of  a  tight  joint 
by  wrapping  a  piece  of  copper  wire  around  the  rubber  tubing 
at  each  end  and  tightening  by  twisting  the  ends  together  with 
the  pliers. 

Water  the  plant  thoroughly  and  make  observations  at  hourly 
intervals,  recording  the  height  of  the  liquid  in  the  tube. 

What  are  your  conclusions  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  9,  10. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  22-24. 


[17] 


EXERCISE  15 
ABSORPTION  BY  A  ROOT 

Materials.  Large  carrot,  beet,  or  other  large  root ;  one-hole  rubber 
stopper ;  glass  tube ;  carpenter's  auger. 

Directions  for  work.  With  the  auger  bore  a  hole  into  the 
upper  end  of  the  root,  nearly  fill  the  hole  with  sugar,  and 
insert  the  stopper.  Place  the  glass  tube  in  the  hole  in  the 
stopper.  Tie  the  stopper  in  with  copper  wire. 

Set  the  root  in  water  and  observe  hourly  for  several  days, 
noting  the  height  of  the  liquid  in  the  tube. 

What  are  your  conclusions  regarding  absorption  by  roots? 

i 
References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  6-11,  79,  80. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  9,  10,  41,  42. 


[18] 


EXERCISE  16 
OSMOSIS 

Materials.  Several  forms  of  apparatus  may  be  used,  choice  being 
largely  a  matter  of  convenience.  The  following  are  suggested : 

1.  A  "diffusion   shell,"  as   sold  by  supply  companies,  may  be 
filled   with    molasses    or   with    sugar   solution,    stoppered   with   a 
one-hole  rubber  stopper  with  glass  tube  inserted,  and 

placed  in  a  vessel  of  water.    Make  the  stopper  tight 
by  wrapping  with  wire  or  waxed  cord. 

2.  A  piece  of  soaked  parchment  paper 
may  be  tied  over  the  large  end  of  a  thistle 
tube  which  has  been  previously  filled  with 
molasses  or  sugar  solution.    The  bulb  of 
the  thistle  tube  should  then  be  immersed 
in  water.    There   is    often   difficulty  in 
preventing  leakage  due  to  the  folds  in 
the  paper. 

3.  The  Lyon  osmometer  shown  in  the 
cut  may  be  assembled,  as  illustrated.    It 

is  cheap,  easily  assembled,  and  certain  in  its  action.    See  apparatus 
list  for  maker. 

Directions  for  work.  Assemble  the  apparatus  chosen  and 
make  hourly  readings. 

Note  that  the  essential  features  are  a  membrane  permeable  to 
water  (parchment  paper),  separating  a  dense  solution  (molasses) 
from  a  much  less  dense  solution  (hydrant  or  well  water). 
What  resemblances  to  a  root  can  you  see  ?  Does  water  tend 
to  move  toward  the  denser  or  toward  the  less  dense  solution 
in  such  cases  as  the  above?  Do  you  know  whether  plant  sap 
contains  substances  in  solution  ?  If  so,  what  substances  are 
known  to  be  sometimes  present  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  79,  80. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  41,  42. 


[19] 


EXERCISE  17 

DOES  THE  FORM  AND  STRUCTURE  OF  THE  ROOT  FAVOR 
ABSORPTION? 

Materials.  Low  covered  glass  dish,  as  a  petri  dish,  and  clean  filter 
paper  or  blotting  paper,  or  drinking  glass  and  filter  paper ;  small 
seeds,  such  as  mustard,  radish,  clover,  or  wheat. 

Directions  for  work.  Place  a  layer  of  blotting  paper  or  several 
layers  of  filter  paper  on  the  bottom  of  a  dish  and  saturate  it  with 
water.  Sow  seeds  thinly  on  the  wet  paper  and  cover.  Set  in 
a  warm  place  several  days,  until  the  roots 
of  the  germinating  seeds  have  reached  the 
length  of  a  half  inch. 

If  preferred,  seeds  may  be  sown  in  the 
fold  of  a  piece  of  filter  paper,  as  illustrated 
in  the  figure.  It  is  necessary  to  provide 
holes  through  the  paper  to  allow  the  roots 
to  grow  down  into  the  water.  These  may 
be  made  with  a  needle. 
Examine  the  roots  without  exposing  them  to  the  air  of  the 
room.  Find  and  identify  the  root  hairs.  Note  their  abundance, 
size,  and  distribution  on  the  roots.  Mount  one  of  the  root  tips 
on  a  slide  and  examine  the  root  hairs  with  the  compound 
microscope,  if  possible. 

In  what  way  might  the  root  hairs  aid  in  the  absorption  of 
water  ? 

References  ' 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  6-9. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  9,  10. 


[20] 


EXERCISE  18 

RELATION  OF  ROOT  HAIRS  TO  SOIL 
Materials.   Seedling  plants  growing  in  sand,  loose  soil,  or  sawdust. 

Directions  for  work.  To  determine  whether  the  root  hairs 
have  any  close  relation  to  the  soil,  gently  remove  a  plant  which 
is  growing  in  very  loose  soil  or  in  sand  or  sawdust.  After 
noting  how  much  soil  adheres,  gently  shake  the  plant  and  note 
results.  Then  wash  the  roots  by  moving  them  to  and  fro  in  a 
vessel  of  water.  Finally,  mount  one  of  the  washed  roots  for 
examination  with  the  hand  lens  or  microscope. 

Do  you  find  that  washing  removes  all  the  soil?  What  is 
your  opinion  regarding  the  original  position  of  the  root  hairs 
with  relation  to  the  soil  particles?  Do  the  root  hairs  appear 
to  be  so  placed  as  to  favor  absorption  of  the  water  which 
moistens  the  surfaces  of  the  soil  particles? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  6-9. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  9,  10. 


[21] 


EXERCISE  19 
COMPOSITION  OF  SOME  PLANT  SUBSTANCES 

Materials.  Dry  starch ;  bits  of  wood ;  test  tubes  ;  bunsen  burner 
or  alcohol  lamp. 

Directions  for  work.  In  the  previous  study  it  has  been  found 
that  plants  take  up  from  the  soil  both  water  and  substances 
dissolved  in  the  water.  Is  the  material  of  which  the  plant  is 
composed  secured  in  this  way  ?  Does  starch,  for  instance,  enter 
the  plant  from  the  soil  in  solution  in  water?  Is  the  wood 
composed  of  materials  which  may  have  entered  in  this  way  ? 
We  may  start  an  investigation  of  these  matters  by  decompos- 
ing plant  materials  to  determine  of  what  they  are  composed. 
Proceed  as  follows: 

Place  a  small  amount  of  dry  starch  in  a  test  tube.  Heat  it 
slowly  over  a  flame.  Does  anything  collect  on  the  sides  of  the 
tube  in  the  upper  and  cooler  part?  So  far  as  you  can  tell, 
what  is  this  substance  ?  Continue  heating  until  the  residue  in 
the  bottom  of  the  tube  no  longer  changes  in  appearance.  Note 
the  black  color  of  this  residue.  It  is  carbon.  Remove  part  of 
it,  if  possible,  and  find  out  whether  it  will  burn. 

When  the  tube  has  cooled,  add  water  and  find  out  whether 
the  carbon  is  soluble  in  water.  Do  you  believe  that  the  carbon 
could  have  entered  the  plant  in  solution  in  water,  through  the 
roots  ?  Is  there,  so  far  as  you  can  learn,  any  large  amount  of 
carbon  in  the  soil?  Is  carbon  commonly  added  to  soils  as  a 
fertilizer  ? 

Repeat  the  experiment  with  chips  of  wood  in  another  test 
tube.  Compare  the  results  in  this  case  with  those  noted  above. 

On  the  basis  of  what  you  have  learned  in  this  experiment, 
does  it  appear  probable  that  all  of  the  materials  which  enter 
into  the  composition  of  a  plant  have  been  secured  from  the  soil  ? 


[22] 


EXERCISE  20 
PRODUCTION  OF  STARCH  IN  LEAVES 

Materials.  Fresh  leaves,  both  green  and  variegated  green  and 
white  (such  as  geranium),  which  have  been  exposed  to  the  sun  for 
several  hours ;  alcohol ;  iodine  solution ;  glass  or  metal  beaker  or 
cup ;  water  bath. 

Directions  for  work.  1.  Dip  each  of  the  leaves  in  boiling 
water  for  a  few  seconds  in  order  to  kill  the  leaf  tissues.  Trans- 
fer them  to  alcohol  in  a  beaker  and  keep  the  alcohol  warm  over 
a  water  bath  for  about  ten  minutes.  When  the  leaves  are 
removed  they  should  be  without  green  color.  Where  has  the 
green  coloring  material  (chlorophyll)  gone  ? 

2.  Place  a  number  of  the  leaves  in  a  weak  solution  of  iodine 
(tincture  of  iodine)  and  allow  them  to  remain  in  the  solution 
about  ten  minutes  or  until  decided  changes  of  color  are  seen. 
Note   the    location    of   the    colored   parts,    particularly   in   the 
variegated  leaves. 

3.  Put  a  small  quantity  of  starch  in  a  test  tube,  add  a  few 
drops  of  iodine  solution,  and  shake  the  tube.    Note  the  result- 
ing color.    Boil  the  water  for  a  few  minutes,  cool,  and  add 
iodine.    Note  color. 

4.  What  substance  did  the  test  reveal  in  the  leaves  ?    Did 
its  location  in  the  variegated  leaves  have  any  relation  to  the 
location  of  the  chlorophyll,  and  if  so,  what  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  15-17. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  37-40. 


[23] 


EXERCISE  21 

THE  CHLOROPLASTS 
i 

Materials.  Thin  leaves  of  a  water  plant,  such  as  Elodea  or  Pota- 
mogeton,  or  leaves  of  a  moss  (these  should  have  been  exposed  to 
direct  sunlight  for  some  hours  before  the  study  is  made)  ;  compound 
microscopes. 

Directions  for  work.  Mount  a  piece  of  a  leaf,  or  pieces  of 
several  leaves,  on  a  slide  for  examination  with  the  microscope. 
Observe  the  cells  of  the  leaf  with  low  power  and  high  power. 

Where  does  the  chlorophyll  occur  in  the  cells  ?  Describe  the 
cells  and  the  chlorophyll  bearers  (chloroplasts). 

To  determine  the  location  of  starch  in  the  leaf  cells,  remove 
the  water  from  the  slide  by  touching  a  piece  of  blotting  paper 
or  filter  paper  to  the  edge  of  the  cover  slip.  Add  dilute  iodine 
at  the  other  edge  of  the  cover.  Examine  the  leaves  for  evidences 
of  starch  and  note  its  relation  to  the  chloroplasts. 

NOTE.  From  the  textbook  it  may  be  learned  that  starch  is  present  in 
the  leaves,  as  shown  by  the  experiment,  because  it  is  manufactured  there. 
Sugar  is  present  for  the  same  reason,  and  more  commonly  than  starch,  but 
there  is  no  equally  convenient  test  for  its  presence.  The  following  exercises 
will  take  up  some  of  the  conditions  necessary  for  the  making  of  such  foods. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  14,  15. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  37. 


[24] 


EXERCISE  22 
IS  LIGHT  NECESSARY  FOR  STARCH-MAKING  IN  LEAVES? 

Materials.  Two  potted  plants,  or  two  small  plants  (as  clover) 
growing -out  of  doors  ;  water  bath ;  beaker  ;  alcohol ;  iodine. 

Directions  for  work.  Put  one  plant  in  a  dark  closet  at  least 
twenty-four  hours  before  the  experiment  is  to  be  performed,  at 
the  same  time  placing  the  other  in  a  window  where  it  is  ex- 
posed to  the  rays  of  the  sun  for  at  least  several  hours  pre- 
ceding the  experiment;  or  if  potted  plants  are  not  available, 
select  two  clover,  plants  in  a  meadow  and  cover  one  of  them 
with  a  bucket. 

Gather  several  leaves  from  each  plant,  remove  the  chlorophyll, 
and  test  for  starch  as  in  Exercise  20. 

What  differences,  if  any,  do  you  find  between  the  leaves 
which  have  been  in  the  dark  and  those  which  have  been  ex- 
posed to  the  light  ?  What  does  this  indicate  about  the  necessity 
of  light  for  starch-making  in  leaves  (photosynthesis)  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  15-17. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  38,  39. 


[25] 


EXERCISE  23 
IS  AIR  NECESSARY  FOR  PHOTOSYNTHESIS? 

Materials.  Plants;  vaseline;  benzine  or  gasoline;  water  bath; 
beaker;  alcohol;  iodine. 

Directions  for  work.  Air  may  be  excluded  from  a  leaf  by 
covering  the  stomata  with  such  a  substance  as  vaseline.  Select 
a  plant  which  has  been  in  the  dark  since  the  previous  day. 
Rub  vaseline  over  the  surfaces  of  several  leaves,  being  particu- 
larly careful  to  completely  cover  the  lower  surfaces.  Place  the 
plant  in  bright  sunshine  for  several  hours. 

When  the  leaves  have  been  exposed  to  the  light  long  enough 
to  have  accumulated  considerable  starch,  remove  the  vaselined 
leaves  and  several  unvaselined  leaves  from  the  plant.  Dissolve 
off  the  vaseline  with  benzine.  Remove  chlorophyll  and  test  for 
starch. 

Compare  the  vaselined  leaves  with  the  unvaselined  leaves, 
noting  the  differences.  What  do  these  differences  mean  ?  What 
is  your  conclusion  about  the  necessity  of  air  for  photosynthesis? 

NOTE.  Air  is  composed  of  several  gases.  This  experiment  does  not 
attempt  to  show  what  part  of  the  air  is  necessary  for  photosynthesis. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  13-17. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  34-39. 
CALDWELL  and  EIKENBERRY.    Elements  of  General  Science,  pp.  65, 
66.    Ginn  and  Company. 


[26] 


EXERCISE  24 
A  WASTE  PRODUCT  OF  PHOTOSYNTHESIS 

Materials.  Submerged  water  plants,  such  as  the  common  pond 
weeds. 

Directions  for  work.  1.  Place  the  plants  in  a  large  glass  jar 
or  aquarium  filled  with  water.  Allow  the  sun  to  shine  upon  it. 
After  ten  minutes  observe  the  plants  and  look  for  evidence 
of  any  gas  escaping  from  the  plants. 
Darken  the  aquarium  and  note  the 
effect.  Try  several  degrees  of  shad- 
ing and  note  effect,  counting  number 
of  bubbles  per  minute,  but  always 
allowing  several  minutes  for  the  new 
conditions  to  produce  its  effect. 

The  gas  escaping  may  be  collected 
by  proper  methods  (see  "  Introduc- 
tion to  Botany,"  Fig.  27)  and  shown 
by  tests  to  be  oxygen,  but  experience 
shows  that  under  laboratory  conditions 
such  tests  are  often  unsatisfactory. 

2.  If  a  good  projection  lantern  is 
available,  the  experiment  may  be  per- 
formed as  follows : 

Place  a  branch  of  a  water  plant  in 
water  in  a  thin  glass  tank,  which  can  be  substituted  for  the. 
slide  carrier.    Illuminate  the  plant  by  the  electric  lamp,  which 
will  project  its  image  upon  the  screen.    After  some  minutes  the 
plant  will  begin  to  give  off  bubbles  of  gas. 

This  method  offers  the  advantage  of  being  available  on  cloudy 
days,  and  the  experiment  may  be  shown  to  all  members  of  a 
large  class  simultaneously. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  15-17. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  38,  39. 


[27] 


EXERCISE  25 

HOW  IS  EXPOSURE  TO  LIGHT  FAVORED  BY  LEAF 
ARRANGEMENT  ? 

Materials.  The  exercise  is  preferably  worked  out  as  a  field  trip, 
but  potted  plants  may  be  used  in  part  if  necessary. 

Directions  for  work.  In  studying  the  arrangement  of  leaves 
with  reference  to  light,  remember  that  light  comes  from  all 
parts  of  the  sky  as  well  as  directly  from  the  sun's  disk.  The 
average  direction  of  light  may  therefore  be  taken  as  approxi- 
mately vertical,  but  it  must  be  remembered  that  much  light 
comes  from  other  parts  of  the  sky  as  well. 

1.  Select  a  vertical  stem  which  is  not  shaded  or  crowded  by 
any  neighboring  stems.    This  may  be  found  on  a  small  tree  or 
shrub,  or  a  weed,  such  as  ragweed,  may  be  used. 

Beginning  at  the  top,  note  the  position  of  each  leaf  blade. 
How  many  leaf  blades  face  a  part  of  the  sky  which  is  within 
45°  of  the  vertical  ?  How  many  of  the  leaves,  when  viewed 
at  right  angles  to  the  surface  of  the  blade,  appear  to  be  shaded 
by  other  leaves  ?  What  proportion  of  the  whole  leaf  surface  of 
the  stem  is  so  shaded  ? 

2.  Select  a  horizontal  stem  on  either  a  creeping  plant  or  a 
nearly  horizontal  branch  of  a  tree.    Note  the  position  of  each 
leaf  and  its  exposure  to  light.    In  this  case  are  the  leaves  dis- 
tributed all  around  the  stem,  as  was  true  of  the  vertical  stem  ? 
If  not,  are  they  in  this  case  attached  to  the  stem  in  different 
positions  from  the  former  example,  or  by  what  means  are  they 
able  to  assume  the  new  positions  ?   If  the  previous  study  (1)  has 
been  made  on  a  tree,   it  is  interesting  to  use  for  this  study 
(2)  another  branch  on  the  same  tree,  making  comparisons  be- 
tween them. 

3.  Examine  a  vine  growing  on  a  wall,  as  the  Boston  ivy. 
Note  that  in  this  case  the  light  from  one  half  of  the  sky  is  cut 
off  by  the  wall.    The  average  direction  of  the  light  reaching 
the  leaves  is  therefore  oblique. 

Supposing  the  light  to  come  to  the  leaves  at  an  angle  of  45° 
from  the  vertical,  how  large  a  part  of  the  leaf  surface  appears 

[28] 


EXERCISE  25  (Continued) 

to  be  in  shadow.  How  much  unoccupied  wall  surface  is  visible 
between  the  leaves.  According  to  your  calculations,  what  per 
cent  efficient  is  the  plant  in  intercepting  the  light  which  comes 
to  the  part  of  the  wall  occupied  by  the  plant  ? 

4.  May  leaves  be  arranged  to  receive  less  than  the  maximum 
amount  of  light? 

Examine  plants  of  prickly  lettuce  growing  in  the  bright  sun- 
shine. Do  the  surfaces  of  the  leaves  face  upwards  ?  What  is 
their  characteristic  position  ?  What  effect  would  this  position 
have  upon  the  intensity  of  illumination  on  the  leaf  surfaces  at 
noon  on  a  bright  summer  day  ? 

If  the  compass  plant  (iSilphium  laciniatum  or  8.  integrifolium) 
grows  in  your  vicinity,  examine  it  also.  Why  has  it  been  called 
the  compass  plant? 

References 

BERGKN  and  CALDWELL.   Practical  Botany,  pp.  55-65. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  69~77. 
Longfellow's  "  Evangeline,"  11. 1216-1221,  refers  to  the  compass  plant. 


[29] 


EXERCISE  26 

HOW  DO  PLANTS  WITHOUT  CHLOROPHYLL  SECURE  THEIR 
FOOD?   A  PARASITE  AS  AN  EXAMPLE 

Materials.  Common  dodder  (Cuscuta),  which  may  be  found  as  a 
field  pest  and  on  wild  plants  in  many  parts  of  the  country.  Other 
dependent  flowering  plants  may  be  substituted  if  more  convenient, 
but  in  this  case  the  directions  must  be  suitably  modified.  Mistletoe, 
beechdrops,  broom  rape,  pinesap,  and  cancer-root  are  examples  of 
parasites  ;  Indian  pipe  is  a  saprophyte.  The  class  should  study  the 
material  in  the  field  if  possible. 

Directions  for  work.  Describe  the  general  characteristics  of 
the  dodder  plant,  such  as  its  size,  color,  presence  or  absence  of 
leaves,  and  manner  of  climbing. 

What  evidences  of  a  dependent  habit  do  you  find  in  the  struc- 
ture, color,  etc.  of  the  dodder  ?  What  evidences  of  a  parasitic 
habit  in  its  connection  with  the  host?  Cut  sections  through 
host  and  parasite  and  by  a  study  of  these  determine  whether 
the  parasite  penetrates  the  host  or  is  merely  adherent  to  the 
outside.  What  evidence  do  you  see  of  any  effect  of  the  parasite 
on  the  host? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  383,  384. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  51-53. 


[30] 


EXERCISE  27 
A  SAPROPHYTE ;  MOLD  AS  AN  EXAMPLE 

Materials.  Package  of  gelatin ;  petri  dishes  or  glass  sauce  dishes 
with  plates  of  glass  for  covers.  Prepare  the  gelatin  for  use  as 
directed  on  the  package  and  pour  enough  in  each  dish  to  cover  the 
bottom  an  eighth  of  an  inch  in  depth.  Cover  with  the  glass  plates. 
Allow  it  to  stand  until  the  gelatin  has  set. 

Directions  for  work.  Transfer  a  little  material  from  a  moldy 
object  to  the  surface  of  the  gelatin  in  the  dishes.  If  possible, 
plant  mold  from  several  sources  in  different  dishes.  Set  the 
dishes  aside  for  several  days  or  until  some  growth  appears. 
Some  of  the  dishes  should  be  placed  in  the  dark.  Observe  from 
day  to  day  and  make  a  daily  memorandum  of  the  facts  observed 
relative  to  each  culture. 

When  the  mold  is  well  grown  make  a  more  careful  study, 
using  hand  lens  or  microscope.  Determine  the  following  facts 
regarding  the  nutrition  of  the  plants : 

Is  there  one  kind  of  mold  or  several  ?  Do  the  molds  possess 
chlorophyll?  Are  they  able  to  manufacture  food?  Do  they 
grow  in  the  dark  as  well  as  in  the  light,  and  what  does  this 
indicate  about  the  source  of  their  food?  Do  the  molds  enter 
the  gelatin  or  have  any  connection  with  it  which  would  indicate 
a  possibility  of  securing  food  from  the  gelatin  ?  Incline  one  of 
the  dishes  and  note  whether  the  consistency  of  the  gelatin  in 
the  vicinity  of  the  mold  patches  indicates  that  the  mold  is 
having  an  effect  upon  the  gelatin.  Do  these  observations  prove 
that  the  mold  feeds  upon  the  gelatin  ? 

Write  a  description  of  the  mold  and  an  account  of  your 
observations  upon  it,  with  such  inferences  as  you  think  are 
justified  by  the  facts  observed. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  213-216. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  234-237. 


[31] 


EXERCISE  28 

WHAT  USE  MAY  THE  PLANT  MAKE  OF  FOOD  MATERIALS, 
SUCH  AS  STARCH? 

Materials.  Pieces  of  green  willow  about  twelve  inches  long  and 
one-half  or  three-eighths  inch  in  diameter ;  quart  fruit  jar. 

Directions  for  work.  Stand  the .  willow  branches  in  the  jar  in 
about  four  inches  of  water.  Place  the  jar  in  a  sunny  window. 
When  roots  are  beginning  to  break  through  the  bark  near  the 
lower  end  of  the  sticks,  girdle  all  of  them  excepting  one  by 
removing  a  narrow  strip  of  bark  all  around  the  stick.  Be  sure 
to  remove  the  bark  clear  to  the  wood.  Some  of  the  pieces  may 
be  girdled  just  above  the  water  level  and  others  at  or  below 
the  surface  of  the  water. 

Watch  the  further  growth  of  roots  above  and  below  the  girdle 
and  compare  with  the  uninjured  branch.  What  effect  upon  the 
growth  of  the  roots  results  from  interruption  of  the  bark  ?  On 
the  supposition  that  the  bark  is  the  principal  path  for  the  trans- 
fer of  food,  what  use  does  the  plant  appear  to  be  making  of 
food  stored  in  the  stem  or  manufactured  by  the  leaves  ?  To 
what  other  similar  purposes  may  food  possibly  be  put  in  the 
plant  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  77-81. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  43-46. 


[32] 


EXERCISE  29 

HOW  MAY  INSOLUBLE  FOODS,  AS  STARCH,  BE  MOVED 
FROM  PLACE  TO  PLACE  IN  THE  PLANT? 

Materials.  Corn  grains  which  have  been  soaked  twenty-four  hours ; 
corn  grains  which  have  germinated  and  grown  sprouts  an  inch  long ; 
young  corn  plants  several  inches  high  with  the  seed  grain  attached ; 
Fehling's  solution ;  iodine  solution. 

Directions  for  work.  Crush  the  soaked  grain  and  boil  it  in 
water  in  a  test  tube.  Pour  part  of  the  resulting  solution  into 
another  tube  and  add  iodine.  Is  there  much  starch  present? 
To  the  remaining  liquid  add  Fehling's  solution  and  bring  to 
boiling.  If  glucose  (a  form  of  sugar)  is  present,  a  copper-red 
or  orange  color  appears  and  the  material  which  produces  the 
color  settles  to  the  bottom  later  as  a  precipitate.  The  amount 
of  sugar  may  be  judged  by  the  amount  of  precipitate  if  suf- 
ficient Fehling's  solution  has  been  added  to  act  on  all  the  sugar. 
A  slight  blue  color  in  the  solution  after  the  precipitate  has 
settled  indicates  that  a  slight  excess  of  Fehling's  solution  has 
been  used. 

Repeat  both  tests  with  germinated  grains  and  with  the  grains 
which  have  been  separated  from  young  corn  plants. 

Note  the  facts  discovered  in  each  test.  What  evidence  do 
you  have  regarding  the  gradual  disappearance  of  the  starch  ? 
What  evidence  of  the  presence  of  sugar  when  starch  is  disap- 
pearing ?  If  starch  can  be  changed  into  sugar,  would  the  trans- 
portation of  this  sort  of  food  material  be  explainable?  How? 

The  experiment  may  be  repeated  with  other  common  seeds. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  78-81. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  40-43. 


[33] 


EXERCISE  30 


DIGESTION  OF  STARCH 

Materials.  Starch  paste ;  malt  extract ;  Fehling's  solution  ;  iodine 
solution  ;  funnel ;  filter  paper  ;  test  tubes. 

To  prepare  the  starch  paste,  place  in  a  test  tube  a  lump  of  starch 
half  as  large  as  a  grain  of  corn,  add  a  small  amount  of  water,  and 
boil  until  all  lumps  have  disappeared  and  a  transparent,  slightly 
milky  fluid  is  obtained.  Dilute  the  starch  paste  thus  obtained  with 
three  or  four  ounces  of  cold  water. 

Crush  a  spoonful  of  germinated  barley  grains  and  soak  in  one  or 
two  ounces  of  water  for  an  hour  or  longer.  Filter  off  the  water  and 
set  it  aside  as  stock  malt  extract. 

Directions  for  work.  To  determine  whether  starch  can  be 
changed  into  sugar  experimentally,  proceed  as  follows:  Select 
four  large  test  tubes  and  label  them  numbers  1,  2,  3,  and  4. 
Place  in  each  about  one  inch  of  the  dilute  starch  paste.  To  num- 
bers 3  and  4  add  about  two  cubic  centimeters  each  of  the  malt 
extract.  Set  all  four  aside  for  at  least  ten  minutes  —  preferably 
an  hour.  At  the  end  of  this  time  treat  each  tube  as  directed 
below  and  record  observations.  Remember  (Exercise  29)  that 
Fehling's  solution  gives  the  test  for  sugar  only  after  boiling. 

What  substance  do  you  know  by  experimental  evidence  to 
be  present  in  the  original  starch  paste  ?  What  is  the  evidence  ? 


TUBE 

ADD 

OBSERVATIONS 

1 

Iodine  solution 

2 

Fehling's  solution 

3 

Iodine  solution 

4 

Fehling's  solution 

[34] 


EXERCISE  30  (Continued) 

What  substance  is  shown  to  be  absent  from  the  original  stock 
of  starch  paste  ?  What  is  the  evidence  ? 

Was  the  substance  which  you  found  in  the  dilute  starch 
paste  present  also  after  the  malt  extract  had  been  added  ?  Was 
any  substance  present  after  malt  extract  was  added  that  was 
not  originally  present  in  the  starch  paste  ?  If  so,  how  do  you 
account  for  its  presence  ? 

Write  a  full  account  of  the  experiment,  giving  your  explana- 
tions of  the  changes  observed  and  the  reasons  for  your  opinions. 

NOTE.  Some  sugar  is  always  present  in  the  malt  extract  and  is  carried 
into  tubes  3  and  4  with  the  malt.  The  relative  amount  may  be  determined 
with  sufficient  accuracy  if  to  an  inch  of  water  in  a  fifth  tube  is  added  malt 
extract  and  Fehling's  solution  in  quantity  equal  to  that  placed  in  tube  4. 
Upon  boiling,  a  red  precipitate  is  formed,  its  quantity  indicating  the 
amount  of  sugar  present  in  the  malt  extract. 

Reference 

BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  46. 


[35] 


EXERCISE  31 

WHAT  PROVISIONS  ARE  MADE  ANNUALLY  FOR  NEXT 
YEAR'S  GROWTH  OF  BRANCHES?   FOOD  STORAGE 

Materials.  Twigs  of  any  common  tree  or  shrub  which  has  large 
buds,  buckeye,  horse-chestnut,  and  some  hickories  are  best;  lilac  is 
common  everywhere  and  is  satisfactory ;  iodine  solution ;  Millon's 
reagent. 

Directions  for  work.  Split  a  twig  and  bud  lengthwise.  Apply 
iodine  to  the  freshly  cut  surface  of  one  half.  Is  there  any  evi- 
dence of  the  presence  of  food  in  the  form  of  starch  ?  Is  the 
quantity  relatively  great  ?  Microscopic  examination  of  thin  cross 
sections  of  the  stem  stained  with  iodine  may  aid  in  estimating 
the  amount  of  starch  present.  Is  starch  principally  in  the  bud 
or  in  the  stem  ? 

In  like  manner  apply  Millon's  reagent  to  the  cut  surface  of 
the  other  half  of  the  twig  and  bud.  This  reagent  produces  a 
red  color,  after  five  or  ten  minutes,  if  protein  is  present.  How- 
ever, since  the  living  substance  in  all  cells  (protoplasm)  is  a 
protein,  the  red  color  may  not  be  taken  to  indicate  stored 
protein  food  unless  the  color  is  pronounced. 

What  are  the  facts  as  you  find  them  regarding  the  reserve 
supply  of  these  two  classes  of  foods  in  the  stem  and  the  bud  ? 

Does  it  appear  to  you  that  the  amount  of  reserve  food  would 
be  sufficient  to  maintain  the  spring  growth  from  the  buds  for 
a  long  time,  or  will  the  new  growth  apparently  soon  depend 
upon  the  manufacture  of  food  by  the  new  leaves?  As  you 
recall  your  observations  of  the  opening  of  buds  and  the  begin- 
ning of  growth  in  spring,  are  the  new  leaves  actually  exposed 
to  the  light  early  or  late  during  the  spring  growth? 

Sum  up  in  your  notes  all  your  observations  of  facts  which 
would  influence  the  new  growth  in  the  spring. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  77,  78. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  43,  44. 


[36] 


EXERCISE  32 

PREPARATION  FOR  NEW  GROWTH  IN  THE   STRUCTURE 
OF  THE  BUD 

Materials.    Twigs  and  buds  as  in  preceding  exercise. 

Directions  for  work.  Examine  a  scaly  bud  in  its  winter  con- 
dition to  discover  what  indications  of  next  spring's  growth  may 
be  found  in  autumn  and  how  the  growing  point  is  protected 
during  the  winter. 

Pick  off  the  scales  one  by  one,  with  care  to  remove  the  entire 
scale  in  each  case.  Note  differences  in  the  scales  as  you  reach 
the  deeper  parts  of  the  bud.  When  the  last  of  the  bud  scales 
has  been  removed,  note  the  central  part  of  the  bud,  which 
represents  the  preparation  for  next  year's  growth.  Can  you 
distinguish  leaves  ?  If  so,  count  them.  Can  you  find  a  stem  ? 
Examine  with  a  hand  magnifier  to  make  sure  on  the  above 
points.  If  leaves  are  found,  distributed  along  a  short  stem,  this 
constitutes  a  miniature  leafy  shoot.  What  changes  would  need 
to  take  place  in  the  spring  to  transform  the  contents  of  the  bud 
into  a  shoot  capable  of  making  food? 

Examine  another  bud  with  reference  to  the  protection  of  the 
growing  point  from  the  unfavorable  conditions  of  winter.  Com- 
pare with  a  longitudinal  section  through  a  bud  (Exercise  31). 
About  what  is  the  thickness  of  the  protective  layer  of  bud 
scales  ?  Do  they  fit  closely  or  loosely  ?  Would  this  thickness 
be  sufficient,  in  your  opinion,  to  keep  the  center  of  the  bud 
above  freezing  temperature  during  a  long  period  of  zero  weather? 
If  possible  to  do  so,  cut  open  buds  out  of  doors  in  severe  weather 
and  note  whether  the  interiors  of  these  buds  appear  to  have 
escaped  freezing.  Would  the  bud  covering  be  effective  in 
delaying  freezing  and  thawing  ? 

Consider  the  need  of '  protection  from  drying.  Is  it  probable 
that  water  would  evaporate  from  an  unprotected  growing  point 
during  cold  weather  ?  Does  water  evaporate  from  other  objects, 
as  from  wet  clothing,  while  frozen  ?  Does  it  seem  probable  that 
water  would  be  supplied  to  the  bud  by  ascending  through  the 
stem  during  very  cold  weather  ?  Why  ?  Is  the  layer  of  scales 

[37] 


EXERCISE  32  (Continued) 

thick  enough  and  do  they  fit  closely  enough  to  greatly  hinder 
evaporation  of  moisture  ?  Examine  several  kinds  of  buds  for 
the  presence  of  gummy  or  varnishlike  substances  which  might 
assist  in  making  the  bud  covering  impervious  to  moisture. 
Compare  growing  tips  which  have  been  exposed  to  the  air  for 
some  time  with  those  from  freshly  opened  buds,  noting  whether 
the  growing  point  actually  wilts  or  dries  more  rapidly  when 
the  protective  covering  is  removed. 

May  protection  from  mechanical  injury  by  the  bud  scales  be 
of  any  importance  ? 

Could  a  structure  similar  to  the  young  shoot  in  the  center 
of  this  bud,  but  without  protecting  scales,  be  called  a  bud? 
Under  favorable  circumstances  might  it  be  able  to  produce  a 
new  shoot,  as  this  bud  does?  Examine  a  geranium  or  other 
house  plant,  and  compare  buds. 

Write  a  careful  account  of  your  observations  and  give  your 
opinion  regarding  the  usefulness  of  the  scales  for  protection 
from  cold,  dryness,  and  mechanical  injury.  Give  reasons  for 
your  opinions,  distinguishing  carefully  between  observed  facts 
and  inferences. 

Make  a  diagrammatic  drawing  of  a  longitudinal  section 
through  a  bud,  showing  the  principal  facts  of  structure. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  90-92. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  94-98. 


[38] 


EXERCISE  33 
THE  OPENING  OF  A  BUD 

Materials.  Trees  and  shrubs  in  the  field.  During  the  winter,  buds 
may  be  caused  to  open  by  standing  cut  branches  in  water,  but  the 
buds  do  not  usually  develop  completely. 

Directions  for  work.  In  spring,  at  the  time  when  buds  are 
about  to  open,  select  a  conveniently  located  tree,  or  several  of 
them,  with  large  buds.  Observe  the  buds  each  day  and  make 
written  notes  of  changes  observed,  examining  the  same  buds 
each  time.  Continue  until  the  shoots  are  several  inches  long. 
A  very  interesting  and  valuable  record  may  be  secured  by  photo- 
graphing the  selected  buds  daily.  The  camera  should  be  close 
to  the  buds  in  order  to  secure  a  large  image. 

What  is  the  history  and  the  final  fate  of  the  scales  ?  When 
the  bud  is  fully  opened,  is  there  left  on  the  twig  any  mark 
which  shows  the  former  position  of  the  scales  ?  Do  the  scales 
on  any  of  the  trees  examined  become  more  leaflike  during  the 
period  of  observation  ? 

What  is  the  history  of  the  growing  shoot  during  the  period 
of  observation  ?  How  many  inches,  or  what  fraction  of  an  inch, 
per  day  does  it  lengthen  when  growing  most  rapidly  ?  Does 
the  number  of  new  leaves  increase  during  this  period  of  rapid 
growth,  or  have  all  the  leaves  been  formed  by  the  time  the 
shoot  emerges  from  the  bud  ?  In  what  way  does  the  new  shoot 
differ  from  older  shoots  on  the  same  tree  ?  Are  there  living 
leaves  on  the  older  parts  of  the  stem  at  this  time  ? 

Enter  your  daily  observations,  with  dates,  in  your  notebook, 
and  write  a  careful  summary  of  the  important  facts  connected 
with  the  opening  of  a  bud. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  chap.  vi. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  chap.  vii. 


[39] 


EXERCISE  34 
THE  HISTORY  OF  THE  GROWTH  OF  A  BRANCH 

Materials.  Twigs  or  short  branches  as  used  in  preceding  exercise. 
This  exercise  is  best  carried  out  in  the  field,  where  branches  may 
be  examined  on  the  trees. 

Directions  for  work.  Examine  several  branches  and  determine 
the  limits  of  last  season's  growth.  This  may  be  readily  de- 
termined by  differences  in  color  and  general  appearance  of  the 
bark.  The  junction  between  the  part  of  the  twig  grown  last 
season  and  the  part  a  year  older  is  marked  by  the  bud-scale 
scars  (Exercise  33).  Aided  by  the  bud-scale  scars,  identify 
each  year's  growth  as  far  back  along  the  branch  as  it  is  possi- 
ble to  distinguish  these  scars.  What  is  the  year  of  growth  of 
the  oldest  section  of  the  branch  the  date  of  which  you  can 
positively  identify  ?  Is  the  amount  of  growth  year  by  year 
practically  uniform  ?  If  not,  can  you  suggest  possible  causes 
for  difference  ? 

Give  attention  next  to  the  conspicuous  and  more  or  less 
crescent-shaped  scars  which  are  distributed  along  the  stem.  They 
are  leaf  scars,  left  when  the  leaves  fell  and  indicating  the 
point  of  attachment  of  leaves.  Compare  with  the  leafy  tips  of 
branches,  or  in  winter  with  house  plants,  to  secure  a  clear 
notion  of  the  relation  of  leaves  to  leaf  scars.  How  many  leaves 
were  on  last  season's  growth-?  How  many  the  preceding  season? 
In  general,  is  the  number  of  leaves  produced  annually  rather 
uniform  or  does  it  vary  widely  ?  The  small  scars  within  the  leaf 
scars  show  where  fibrovascular  bundles  passed  into  the  leaves. 

Reexamine  the  stem  with  reference  to  character  and  location 
of  buds.  In  addition  to  the  large  bud  at  the  end  of  each  twig 
(terminal  bud)  which  was  studied  in  some  of  the  preceding 
exercises  there  are  usually  many  buds  scattered  along  the  sides 
of  the  twigs.  These  are  called  lateral  buds.  What  is  the  posi- 
tion of  the  lateral  buds  with  reference  to  the  leaf  scars?  What 
was  their  relation  to  the  leaves?  Are  they  formed  while  the 
leaves  are  yet  on  the  branches  or  after  the  leaves  have  fallen  ? 
If  you  have  watched  the  opening  of  buds  in  spring  (Exercise  33), 

[40] 


EXERCISE  34  (Continued) 

have  you  found  that  the  lateral  buds  open  ?  If  so,  what  do  they 
produce  ?  On  the  older  parts  of  the  branch  which  you  have 
been  examining  are  there  any  evidences  of  growth  from  lateral 
buds  ?  What  have  the  lateral  buds  produced  ?  Determine,  by 
examination  of  the  twig,  when  each  of  these  buds  began  to 
grow.  Do  the  buds  open  during  their  first  season ;  that  is,  with- 
out having  spent  a  winter  in  the  resting  condition  ? 

Other  well-marked  scars  are  often  found  on  branches.  These 
may  be  scars  left  by  fruit  or  flowers,  and  they  vary  greatly  in 
size  and  position  in  different  kinds  of  trees.  Scars  due  to 
injuries  may  be  present  also. 

Draw  a  line  to  represent  the  branch  you  have  been  studying 
and  mark  the  end  of  each  year's  growth.  Indicate  in  figures 
the  year  in  which  each  section  grew.  In  like  manner  add  the 
secondary  branches  and  indicate  their  annual  growth. 

Set  down  in  your  notes  all  the  facts  to  which  your  attention 
has  been  called  in  this  study  or  which  you  have  observed  in- 
dependently. '  Then  write  a  connected  story  of  the  growth  of 
the  particular  branch  you  have  been  studying. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  chap.  vi. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  chap.  vii. 


[41] 


EXERCISE  35 
SOME  EXAMPLES  OF  EXTENSIVE  STORAGE  OF  FOODS 

Materials.  Tubers  of  potato  or  Jerusalem  artichoke ;  bulbs  of 
onion  or  hyacinth ;  some  carrots,  parsnips,  turnips,  sweet  potatoes, 
or  radishes;  eosin;  iodine;  Fehling's  solution ;  Millon's  reagent. 

Directions  for  work.  1.  Cut  open  a  tuber  and  test  several 
parts  of  the  interior  for  stored  foods,  using  the  tests  with  which 
you  are  familiar  from  preceding  exercises.  Does  food  material 
appear  to  be  relatively  abundant  ?  Is  it  generally  distributed 
throughout  the  tuber  ?  What  kind  of  food  material  appears  to 
be  most  abundant  ?  In  textbooks  of  human  physiology  or 
home  economics  look  up  the  composition  of  the  potato,  noting 
especially  the  proportion  of  proteins  and  carbohydrates.  Do 
your  conclusions  correspond  to  the  analysis  given?  Why  are 
potatoes  a  valuable  article  of  food  for  men  ?  What  use  is  made 
of  the  stored  food  by  the  potato  plant? 

Tubers  are  said  to  be  very  much  thickened  stems.  Can  you 
prove  or  disprove  this  ?  Examine  the  exterior  of  the  tuber  for 
such  features  as  you  found  on  stems  (Exercise  34).  Are  there 
buds  present,  as  indicated  by  their  readiness  to  grow  into  new 
shoots  and  by  budlike  structure  (Exercises  31,  32)  ?  Can  you 
identify  the  terminal  bud  ?  Is  there  anything  which  corresponds 
to  leaves  ?  Review  the  previous  exercises,  or  the  textbook,  to 
refresh  your  mind  regarding  the  exact  position  of  leaves  with 
relation  to  buds,  and  note  that  as  the  tuber  is  underground, 
any  leaves  found  upon  it  might  differ  very  much  from  ordinary 
foliage  leaves. 

To  determine  the  location  of  fibrovascular  tissues,  cut  off 
a  slice  of  the  tuber  at  the  opposite  end  from  the  terminal 
bud  and  stand  the  tuber  on  the  cut  end  in  red  ink  or  eosin 
solution.  After  twenty-four  hours  cut  cross  and  longitudinal 
sections  and  trace  the  fibrovascular  bundles.  Can  you  trace 
the  fibrovascular  bundles  out  to  the  structures  suspected  of 
being  buds  ? 

2.  Examine  a  bulb  for  stored  food  as  the  tuber  was  examined, 
using  the  outline  and  questions  given  under  1. 

[42] 


EXERCISE  35  (Continued) 

Investigate  the  structure  of  the  bulb  by  removing  the  scales 
one  by  one,  as  you  did  when  you  studied  the  bud.  In  what 
respects  does  the  bulb  resemble  a  bud  ?  In  what  respects  does 
it  differ?  How  does  the  amount  of  food  stored  in  the  bulb 
compare  with  that  stored  in  a  bud  ?  Is  the  food  in  the  bulb 
stored  in  the  new  shoot  or  in  the  scales? 

3.  In  a  similar  manner  study  one  of  the  enlarged  roots. 
Note  that  while  the  enlarged  part  of  the  carrot,  parsnip,  etc.  is 
principally  root,  yet  the  upper  part  bears  leaves  and  is  there- 
fore stem.  The  sweet  potato  is  a  root  only. 

Compare  roots  such  as  these  with  roots  of  common  annual 
plants,  as  ragweed,  to  secure  a  notion  of  the  comparative 
enlargement. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  chap.  v. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  87-89. 


[43] 


EXERCISE  36 

THE  USE  MADE  OF  STORED  FOOD 
Materials.    Mature  turnips,  carrots,  parsnips,  or  beets. 

Directions  for  work.  Plant  several  turnips  or  other  thickened 
roots  in  the  garden  in  the  spring,  allowing  them  to  grow  until 
they  "  go  to  seed."  Note  the  rapidity  with  which  the  first 
leaves  and  the  erect  stem  are  formed,  compared  with  the  rate 
of  growth  from  seed. 

When  the  plants  have  set  seed,  dig  up  one  and  cut  open  the 
root.  Has  it  remained  firm  ?  Make  the  usual  food  tests.  Does  it 
contain  as  large  an  amount  of  food  as  when  planted  ?  Examine 
several  other  roots  to  see  whether  the  facts  you  find  in  one  are 
characteristic  of  all. 

In  autumn  it  is  usually  possible  to  find  in  gardens  old 
radishes  which  have  produced  seed  as  well  as  many  younger 
radishes.  It  is  then  possible  to  make  the  above  study  by  direct 
comparison,  without  growing  the  plants. 

On  the  basis  of  the  above  study  do  you  find  that  the  stored 
food  may  be  used  by  plants  ?  If  so,  for  what  purpose  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  33-35. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  43-46. 


[44] 


EXERCISE  37 


HOW  DOES  THE  AMOUNT  OF  AVAILABLE  STORED  FOOD 
AFFECT  GROWTH? 

Materials.  Old  potatoes.  Potato  tubers  will  not  sprout  readily 
soon  after  being  dug.  If  the  exercise  is  performed  in  the  autumn, 
the  tubers  to  be  used  should  be  some  that  have  been  stored  for  some 
time,  preferably  in  a  cold  place. 

Directions  for  work.  Cut  one  of  the  tubers  into  two  pieces 
crosswise,  split  another  from  end  to  end,  and  cut  several  others 
into  various-sized  smaller  pieces.  Cut  several  pieces  so  as  to 
include  only  one  eye  and  very  little  food  reserve ;  cut  several 
others  with  one  eye  and  as  much  stored  food  as  possible ;  secure 
several  pieces  without  eyes,  and  some  pieces  with  several  eyes 
to  the  piece.  It  would  add  exactness  to  the  experiment  if  the 
pieces  selected  for  planting  were  weighed. 

Plant  the  pieces  of  tubers  in  a  garden,  if  the  study  is  made 
in  the  spring,  or  in  a  box  of  clean  sand  in  the  laboratory.  Put 
a  small  numbered  stick  by  each  piece  planted  and  record  in  your 
notebook  the  descriptions  of  the  pieces. 

Make  daily  memoranda  of  the  growth  of  the  sprouts  as  soon 
as  they  appear  above  the  soil.  When  it  appears  evident  that  no 
more  will  come  up,  dig  up  all  the  pieces  planted  and  lay  them 
in  a  row  on  the  table  for  inspection.  Tabulate  the  facts  as 
follows : 


NUMBER 

SIZE  ou 
WEIGHT 

NUMBER  OF 
EYES 

NUMBER  OF 
SPROUTS 

TOTAL  LENGTH 
OF  SPROUTS 

REMARKS 

• 

* 

[45] 


EXERCISE  37  (Continued) 

Is  every  part  of  the  surface  of  a  potato  able  to  give  rise  to 
a  sprout  ?  What  part  of  the  potato  is  necessary  for  the  pro- 
duction of  a  sprout  ?  From  how  small  a  piece  did  you  succeed 
in  securing  growth?  Does  more  than  one  eye  commonly  grow 
when  several  are  present  ?  What  is  the  relation  of  amount  of 
stored  food  to  vigor  and  amount  of  growth? 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  82-85. 

BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  44-46,  87-89. 


[46] 


EXERCISE  38 


FIELD  STUDY  OF  FOOD  STORAGE 
Materials.    Various  early  spring  plants  in  the  field. 

Directions  for  work.  In  the  early  spring,  when  plants  are 
beginning  growth,  note  which  ones  make  a  very  rapid  growth, 
as  shown  by  the  formation  of  large  and  numerous  leaves  within 
a  few  days  or  by  very  early  flowering.  Examine  the  under- 
ground parts  of  these  plants  and  note  in  how  large  a  proportion 
of  cases  you  find  evidence  of  food  storage. 

Tabulate  your  observations  as  follows,  giving  the  name  of 
the  plant  in  each  case  (if  known),  the  kind  of  food-storage  organ 
(as  tuber,  bulb,  root,  etc.),  and  the  relative  amount  of  storage. 


NAME 


KIND  OF  ORGAN 


RELATIVE  AMOUNT 
OF  STORAGE 


REMARKS 


What  do  you  find  to  be  the  relation  between  storage  and 
early  spring  growth? 

Reference 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  491,  492. 

[47] 


EXERCISE  39 
VEGETATIVE  REPRODUCTION  BY  STOLONS  AND  RUNNERS 

Materials.  Blackcap  raspberry  plants  and  strawberry  plants  in 
place  in  the  garden. 

Directions  for  work.  1.  Stolons.  When  the  new  raspberry  canes 
which  come  up  each  spring  have  become  long  enough  to  droop 
considerably  at  the  ends,  bend  some  of  them  down  so  that  the 
tips  are  in  contact  with  the  soil,  which  should  be  loosened  up 
somewhat  at  that  point.  Fasten  each  branch  down  by  laying 
a  clod  of  earth  on  each  one  or  by  pinning  down  with  a  forked 
stick.  Examine  from  time  to  time,  noting  how  the  stem  tip 
establishes  connection  with  the  soil  and  forms  a  new  plant. 

In  a  group  of  black  raspberries  such  reproduction  as  the 
above  commonly  occurs  naturally,  and  examples  may  be  found 
without  difficulty.  Early  in  the  spring  the  plants  that  have 
been  thus  formed  during  the  preceding  season  may  be  separated 
from  the  parent  plant  and  transplanted. 

Write  a  full  description  of  the  formation  of  new  plants  by 
this  method. 

2.  Runners.  Examine  strawberry  plants  after  the  fruiting 
season  is  past,  which  in  most  parts  of  the  country  may  be  in 
July.  Do  you  find  any  tendency  to  form  new  plants  by  the 
rooting  of  branches  in  contact  with  the  soil  ?  Are  these  branches 
foliage  branches  of  the  usual  type,  as  in  the  raspberry,  or  are 
they  special  branches  having  reproduction  as  their  principal  office  ? 

Write  an  account  of  your  observations. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  p.  85. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  90. 


[48] 


EXERCISE  40 

REPRODUCTION  FROM  LEAVES 
Materials.    Leaves  of  bryophyllum.  plant. 

Directions  for  work.  Remove  several  leaves  from  the  plant 
and  lay  them  on  soil  or  sand.  After  several  weeks  a  number 
of  small  plants  will  be  found  growing  at  the  edges  of  each 
leaf.  When  these  are  well  rooted  they  may  be  separated  from 
the  leaf  and  transplanted. 

Some  other  leaves,  as  those  of  gloxinia  and  begonia,  will 
reproduce  in  a  similar  manner  but  not  so  readily  as  bryophyllum. 
Begonia  leaves  occasionally  produce  small  plants  while  still 
attached  to  the  plant. 

Reference 

BERGEN  and  CALDWELL.   Practical  Botany,  p.  89. 


[49] 


EXERCISE  41 
REPRODUCTION  FROM  ROOTS 

Materials.  Locust  or  silver-leaved  poplar  trees  which  are  sending 
up  "  sprouts  "  at  some  distance  from  the  parent  trees. 

Directions  for  work.  Select  young  sprouts,  preferably  not 
over  two  feet  tall,  and  dig  away  the  earth  about  their  bases 
until  the  connection  with  the  parent  plant  is  reached.  Do  they 
arise  from  undoubted  roots  ?  Do  they  arise  at  the  end  of  a  root 
or  along  its  course  ?  Is  there  any  reason  for  thinking  that  they 
might  be  able  to  continue  growing  if  connection  with  the  parent 
plant  were  interrupted?  Sever  the  main  root  between  the 
sprout  and  the  parent  plant,  carefully  replace  the  earth,  and 
note  whether  the  sprout  shows  signs  of  wilting  within  a  few 
days;  or  if  the  study  is  before  growth  begins  in  the  spring, 
note  whether  the  shoot  is  able  to  leaf  out  as  others  do. 

NOTE.  A  number  of  other  trees  and  some  shrubs  reproduce  from  the 
roots,  especially  if  the  roots  are  wounded.  Sweet  potatoes  are  propagated 
from  the  fleshy  roots. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  p.  33. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  32. 


[50] 


EXERCISE  42 

PROPAGATION  BY  ROOTS 
Materials.    Roots  of  horse-radish. 

Directions  for  work.  Cut  off  the  upper  ends  of  the  roots,  thus 
removing  all  stem  tissues  and  buds.  Cut  the  roots  into  pieces 
of  various  sizes.  Plant  the  pieces  in  soil  or  sand  and  keep 
moist.  When  signs  of  growth  are  seen,  dig  up  the  roots  and 
examine  them. 

Are  buds  and  shoots  formed  freely  by  the  roots  ?  Are  small 
pieces  of  roots  able  to  form  shoots  ?  What  would  be  the  result 
of  breaking  up  the  roots  of  a  horse-radish  plant  in  the  soil,  as 
by  plowing  ?  Does  this  assist  in  explaining  why  horse-radish  is 
such  a  persistent  weed  ? 

References 

BERGEX  and  CALDWELL.   Practical  Botany,  p.  33. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  32. 


[51] 


EXERCISE  43 
PROPAGATION  BY  SOFTWOOD  CUTTINGS 

Materials.  Make  cuttings,  or  "  slips,"  by  cutting  off  the  tips  of 
branches  of  the  geranium  with  a  sharp  knife.  Each  cutting  should 
be  about  three  inches  long. 

Directions  for  work.  Remove  all  the  leaves  except  a  few 
of  the  smallest  ones.  Make  a  trench  about  an  inch  deep  in  the 
sand  and  stand  the  cuttings  upright  in  the  trench.  Fill  the 
trench  and  press  the  sand  closely  about  the  bases  of  the  cut- 
tings. Moisten  the  sand  well  and  place  the  box  in  the  light, 
but  protect  the  cuttings  from  the  direct  rays  of  the  sun  for 
several  days.  The  sand  must  be  kept  warm. 

After  the  first  week  examine  every  second  or  third  day  by 
lifting  one  or  two  cuttings  from  the  box,  together  with  a  small 
amount  of  sand.  This  must  be  done  carefully  in  order  to  avoid 
breaking  the  roots.  The  sand  may  be  removed  gently  and  the 
growth  of  the  roots  noted. 

When  the  roots  are  two  inches  long  the  sand  may  be  washed 
from  the  roots  of  one  or  two  cuttings  to  allow  of  more  careful 
study.  From  what  part  of  the  stem  do  the  roots  grow  ?  Do 
they  come  from  the  cut  surface  or  from  the  sides  of  the  stem  ? 
Has  the  cut  healed  or  changed  in  any  way  ?  Has  the  leaf  surface 
increased  during  the  experiment  ?  Why  was  it  necessary  to 
remove  most  of  the  leaf  surface  at  first? 

If  any  cuttings  are  unused  when  the  study  is  completed,  they 
may  be  transplanted  to  pots  of  earth  and  allowed  to  grow  for 
some  time,  after  which  they  may  be  taken  home  by  the  pupils 
or  used  to  plant  the  school  grounds. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  p.  86. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  p.  90. 


[52] 


EXERCISE  44 


CLEFT  GRAFTING 

Materials.  An  apple  tree  upon  the  branches  of  which  it  is  desired 
to  graft  another  variety  ;  scions  of  the  desired  variety  ;  saw ;  sharp 
pocket  knife  ;  hammer  and  chisel ;  grafting  wax. 

Grafting  wax  may  commonly  be  purchased  from  stores  which 
deal  in  garden  and  orchard  supplies,  but  it  may  also  be  prepared  in 
the  laboratory  without  difficulty.  One  method  given  is  as  follows : 

Common  rosin        7  parts 

Beeswax 2  parts 

Beef  tallow 1  part 

Melt  the  ingredients  together  over  a  slow  fire,  stirring  thoroughly 
until  well  mixed.  Then  pour  the  melted  mass  into  a  pail  or  tub  of 


Two  Methods  of  Grafting 

cold  water.  Grease  the  hands  with  tallow,  and  with  the  hands  work 
the  mass  together  in  the  water.  As  soon  as  it  is  cool  enough  to  stick 
together  remove  it  from  the  water  and  pull  like  taffy  until  it  has 
changed  color  decidedly  'and  becomes  too  stiff  to  work.  Roll  it  into 
balls  and  store  away  for  future  use,  as  it  will  keep  indefinitely. 

Directions  for  work.  A  scion  is  a  cutting  from  a  twig  of  a 
tree  which  is  to  be  used  for  grafting  purposes.  The  twigs  must 
be  cut  from  the  trees  while  in  the  dormant  condition  ;  that  is, 

[53] 


EXERCISE  44  (Continued) 

between  leaf-fall  in  autumn  and  resumption  of  growth  in  spring. 
The  best  practice  is  to  cut  them  before  the  first  freeze  in  autumn 
and  store  them  in  green  sawdust  in  the  cellar  until  they  are 
wanted.  They  must  not  be  allowed  to  become  dry.  The  scions 
should  be  cut  from  healthy  twigs  with  firm,  well-matured  wood. 
The  twigs  should  not  be  less  than  five  or  six  inches  long. 

Cleft  grafting  is  done  in  the  spring  before  growth  starts. 
Saw  off  a  branch  which  is  one  or  two  inches  in  diameter  and 
split  the  stub  down  the  center  with  a  strong  knife.  Prepare 
the  scion  by  cutting  it  down  to  four  or  five  inches  in  length 
and  whittling  the  lower  end  to  a  wedge  shape.  The  wedge 
should  be  at  least  one  inch  long,  tapered  evenly  on  both  sides, 
and  smoothly  cut. 

With  a  knife  or  chisel  pry  open  the  cleft  which  has  been 
made  in  the  stub  and  insert  the  wedge-shaped  end  of  the  scion, 
placing  it  so  that  the  bark  of  one  side  of  the  scion  will  be  in 
contact  with  the  inner  bark  of  the  stub  (stock).  Remove  the 
chisel  and  allow  the  cleft  to  close  upon  the  scion  and  hold  it 
in  position.  Melt  some  wax  and  daub  it  over  the  cut  surfaces, 
sealing  them  from  the  air  completely. 

If  the  stub  of  the  stock  has  a  diameter  greater  than  two 
inches,  it  may  be  advisable  to  set  two  scions,  in  which  case  the 
weaker  one  should  be  cut  out  a  year  later. 

Examine  grafts  a  year  or  more  old  and  note  how  growth 
from  the  scion  has  occurred  and  how  healing  of  the  wound  has 
proceeded.  Why  is  it  necessary  to  set  the  scion  exactly  in  the 
position  directed  above  ?  Why  not  set  it  in  the  center  of  the 
stub  ?  Make  several  grafts  with  the  scion  in  a  variety  of 
positions  and  note  results. 

NOTE.  Top  grafting  by  the  method  described  above  may  be  employed 
with  many  trees  9ther  than  the  apple.  It  is  entirely  practicable  to  graft  a 
large  number  of  varieties  of  apple  upon  a  single  stock,  thus  producing  results 
that  are  very  curious  and  interesting,  though  not  commercially  important. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  87-89. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  91-93. 

[54] 


EXERCISE  45 


BUDDING 

Materials.  Seedling  peach  trees  not  over  one  year  old,  to  be  used 
as  the  stock;  well-grown  leafy  peach  twigs  of  the  season,  of  some 
desirable  variety ;  sharp  knife ;  strips  of  raffia. 

Directions  for  work.  Budding  is  usually  done  in  late  summer, 
the  exact  time  depending  upon  the  latitude.  In  the  southern 
parts  of  the  country  it  may  be  done  in  June,  but  in  more 
northern  latitudes  not  before  the  last  week  in  August.  In 
any  case  the  budding  must  be  clone  while  growth  is  vigorous. 


At  a  point  on  the  stock  two  or  three  inches  above  the  ground 
make  a  cut  through  the  bark,  but  no  deeper,  and  about  half- 
way round  the  stem.  From  the  center  of  this  cut  make  another 
extending  downward  about  an  inch.  Gently  lift  the  bark  with 
the  knife  point  and  slightly  turn  back  the  two  flaps  formed. 
The  bark  should  peel  readily. 

Select  a  leafy  twig  of  the  variety  which  it  is  proposed  to 
graft  upon  the  stock  and  cut  off  a  number  of  leaves,  allowing 
a  half  inch  or  more  of  the  petiole  to  remain  attached  to  the 
twig  (called  a  "  budding  stick  ").  With  the  knife  cut  into  the 
twig  below  the  selected  bud  and  continue  the  cut  upward  under 
the  bud  in  such  manner  as  to  raise  a  triangular  shaving,  with 
its  broader  end  remaining  attached  and  the  bud  situated  near 
its  middle.  Make  a  crosscut  through  the  bark  just  above  the 
bud.  The  bud  and  its  attached  triangular  piece  of  bark  may 


EXERCISE  45  (Continued) 

then  be  peeled  from  the  wood  and  inserted,  pointed  end  first, 
under  the  flaps  of  bark  on  the  stock.  The  stub  of  the  leaf 
petiole  will  serve  as  a  handle  in  manipulating  the  bud.  The 
bud  should  be  pushed  down  under  the  flaps  of  bark  until  the 
upper  edge  of  bark  attached  to  the  bud  abuts  against  the  bark 
on  the  stock.  Press  the  graft  into  good  contact  with  the  wood 
by  wrapping  with  a  strip  of  raffia. 

If  at  the  end  of  ten  days  the  petiole  stub  below  the  engrafted 
bud  remains  green,  it  may  be  supposed  that  the  graft  has 
formed  a  union  with  the  stock.  The  raffia  should  then  be  re- 
moved by  cutting  it  on  the  side  opposite  the  bud.  If  budded 
in  the  autumn*  no  growth  is  to  be  expected  before  the  next 
spring.  The  stock  should  then  be  cut  off  just  above  the  bud. 

Budding  may  also  be  employed  in  top  grafting  older  trees. 
Many  kinds  of  trees  besides  peach  are  commonly  budded.  The 
seedless  orange  trees,  for  instance,  are  budded  upon  sour  orange 
trees  or  upon  lemon  trees. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  87-89. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  81-83. 


[56] 


EXERCISE  46 
THE  PARTS  OF  A  FLOWER 

Materials.  Any  fairly  large  flower  that  can  be  secured  in  the 
autumn  excepting  the  composites,  such  as  goldenrod,  aster,  chrysan- 
themum, and  dandelion.  Flowers  of  house  plants,  if  not  "  double," 
may  be  used. 

Directions  for  work.  By  the  aid  of  the  textbook  identify 
sepals,  petals,  stamens,  pistil,  receptacle.  Identify  also  the  parts 
of  the  pistil  —  ovary,  style,  stigma.  Beginning  at  the  outside  of 
the  flower,  pick  off  each  of  the  parts  of  the  flower,  noting  where 
it  is  attached,  its  relations  to  the  other  parts,  and  its  form  and 
color.  When  you  have  satisfied  yourself  that  you  know  the 
relation  of  the  different  parts  to  each  other,  make  a  floral 
diagram  showing  an  ideal  vertical  section  through  the  flower 
and  another  showing  the  plan  of  the  flower.  These  are  com- 
monly known  as  vertical  diagrams  and  horizontal  diagrams.  In 
making  the  horizontal  diagrams  draw  the  circle  upon  which 
the  diagram  is  built  with  a  compass.  Use  the  same  shapes 
and  shading  to  represent  petals,  sepals,  etc.  as  are  used  in  the 
figures.  Be  careful  to  make  the  diagrams  symmetrical. 

After  having  completed  the  study  of  the  first  flower,  examine 
several  others,  making  floral  diagrams.  At  least  five  should  be 
studied. 

Compare  the  series  of  completed  horizontal  diagrams.  Is  the 
number  of  sepals  the  same  in  all  the  flowers  studied?  What 
are  the  most  common  numbers  ?  In  the  flower  first  studied  are 
the  petals  of  the  same  number  as  the  sepals,  or  a  multiple  of 
the  same  number,  or  is  the  number  of  petals  wholly  unrelated 
to  the  number  of  sepals  ?  What  is  the  number  of  stamens,  and 
how  does  it  compare  with  the  number  of  sepals  and  petals  ? 
Can  you  detect  any  numerical  plan  in  the  flower? 

Study  each  of  the  horizontal  diagrams  in  turn  with  reference 
to  the  numerical  plan. 

Compare  the  vertical  diagrams  with  reference  to  the  attach- 
ment of  the  several  organs  of  the  flower.  In  the  first  flower 
studied  are  the  sepals  inserted  upon  the  receptacle  ?  Are  the 

[57] 


EXERCISE  46  (Continued) 


3  a,  Ranunculus :  horizontal  diagram 
b,  Ranunculus:  vertical  diagram 

4  a,  Hyadnthus  :  horizontal  diagram 
0  L         4b,  Hyadnthus :  vertical  diagram' 

la,  Sdtta:  horizontal  diagram 

1  b,  Sdtta :  vertical  diagram.  \—\STA  MENS 

,,    .  .    ,.  WWMfaCARPELS 

2d,  Cineraria:  horizontal  diagram    m^rmRECEPTACLE 


5b 


^a>  Nareiasus  •'  horizontal  diagram 
&b,  Narcissus:  vertical  diagram 
6  a,  Abuitton  :  horizontal  diagram 
t.-~::-\FWRA  L  TUB$     p  6,  AbutUon  :  vertical  diagram 


St  b>  Cineraria  :  vertical  diagram 

After  Choate,  in  School  Science  and  Mathematics,  Vol.  XIV,  p,  140 

petals  inserted  on  the  receptacle  ?   If  not,  where  are  they  in- 
serted ;  that  is,  from  what  part  of  the  flower  do  they  appear  to 
spring  ?  What  do  you  observe  about  the  insertion  of  the  stamens  ? 
Study  each  of  the  vertical  diagrams  in  like  manner. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  chap.  vii. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  chap.  ix. 

[58] 


EXERCISE  47 
HOW  ARE  SEEDS  AND  FRUIT  FORMED  FROM  THE  PISTIL? 

Materials.  Tomato  flowers  and  fruits  in  all  stages  of  develop- 
ment, from  the  newly  opened  flower  to  the  ripe  fruit.  The  small 
and  unimproved  varieties,  as  the  cherry  tomato,  are  much  to  be 
preferred  to  the  improved  garden  varieties.  Many  other  fruits,  as 
ground  cherry,  wild  nightshades,  lemon,  orange,  apple,  and  pear, 
may  be  used  for  this  or  similar  studies. 

Directions  for  work.  Make  floral  diagrams,  both  vertical  and 
transverse,  showing  the  relative  position  of  all  the  floral  organs. 
Include  a  cross  section  of  the  ovary  in  your  diagrams  or  draw 
it  separately. 

Arrange  the  tomato  fruits  in  order  of  age,  judging  by  relative 
size  and  general  appearance.  By  studying  them  in  succession 
find  out  what  becomes  of  each  of  the  parts  of  the  flower.  Make 
a  series  of  two  or  more  vertical  diagrams  showing  these  facts. 

Make  cross  sections  of  the  fruits  in  different  stages  of  de- 
velopment and  represent  in  diagrams  the  changes  which  take 
place  in  the  internal  parts  of  the  fruits. 

Write  briefly  the  story  of  the  development  of  the  fruit  from 
the  flower. 

Any  other  plant  which  bears  flowers  and  fruits  at  the  same 
time  may  be  used.  Evening  primrose  and  the  peas  and  beans 
are  suggested. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  111-114. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  130-132. 


[59] 


EXERCISE  48 
HOW  IS  POLLEN  CARRIED  FROM  STAMEN  TO  STIGMA? 

Materials.  A  variety  of  wild  or  garden  flowers  growing  undis- 
turbed; hand  magnifier. 

Directions  for  work.  This  is  a  field  study.  If  flowers  and 
insects  are  not  abundant  at  the  time  this  exercise  would  natu- 
rally be  taken  up,  this  and  several  following  exercises  may  be 
postponed,  together  •  with  the  corresponding  parts  of  the  text- 
book, until  a  suitable  time  in  the  spring  of  the  year.  This 
exercise  might  appropriately  follow  Exercise  105. 

Select  a  location  where  flowers  of  several  kinds  are  abundant. 
Visit  the  place  early  in  the  morning  and  observe  the  visits  of 
insects  to  the  flowers.  Selecting  a  group  of  flowers  which  appear 
to  attract  insects  in  abundance,  observe  closely  the  actions  of  the 
insects,  noting  how  they  enter  a  flower,  how  they  leave  it,  and 
whether  they  come  in  contact  with  pistil  and  stamens.  Does  any 
pollen  adhere  to  the  body  of  the  insect  ?  Is  there  any  probability 
that  pollen  is  transferred  from  stamen  to  stigma  in  the  same 
flower  ?  Does  the  insect  visit  flowers  of  the  same  kind  in  succes- 
sion, or  does  he  go  from  one  kind  to  another  at  random  ?  What  is 
the  importance  of  this  point  ?  Examine  stigmas  in  flowers  that 
have  been  visited  by  insects  and  try  to  ascertain  whether  there 
is  pollen  on  the  stigmas.  It  would  also  be  of  interest  to  inclose 
opening  buds  in  paper  bags  in  order  to  prevent  visits  of  insects, 
and  to  note  whether  pollen  is  found  on  stigmas  in  these  cases.  So 
far  as  you  can  tell,  do  the  visits  of  insects  result  in  pollinating 
the  stigmas?  Does  pollination  appear  to  be  accomplished  with 
pollen  from  the  same  flower  (self-pollination)  or  with  pollen  from 
other  flowers  (cross-pollination)  ?  How  great  is  the  probability 
that  cross-pollination,  either  with  or  without  self-pollination, 
occurs  in  practically  all  of  the  flowers  visited  by  insects. 

Make  a  study  of  such  other  flowers  as  may  be  found  in  the 
vicinity,  noting  for  each  such  facts  as  are  suggested  below: 

1.  Kinds  of  insects  visiting  each. 

2.  Number  of  individual  insects  visiting  a  given  cluster  in  a 
given  number  of  minutes. 

[60] 


EXERCISE  48  (Continued) 

3.  Characteristic  actions  of  the  insects  in  visiting  each  kind 
of  flower. 

4.  Peculiarities  in  the  form  of  the  flowers  which  tend  to  insure 
pollination. 

5.  Any    characteristics    of   the   flowers   which    favor   cross- 
pollination  rather  than  self-pollination. 

References 

BERGEN  and  CALDWELL    Practical  Botany,  chap.  viii. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  137-154. 
LUBBOCK.   Flowers,  Fruits,  and  Leaves,  chaps,  i  and  ii.  The  Macmillan 
Company. 


[61] 


EXERCISE  49 
PREVENTION  OF  SELF-POLLINATION  BY  DICHOGAMY 

Materials.  Flowers  in  the  field,  or,  if  necessary,  the  flowers  may 
be  brought  into  the  laboratory. 

Directions  for  work.  By  dichogamy  is  meant  the  maturing  of 
stamens  and  stigma  in  a  flower  at  different  times.  The  maturity 
of  the  stamen  may  be  judged  by  the  shedding  of  the  pollen ; 
most  stigmas  have  a  moist  surface  at  the  time  that  the  pistil  is 
ready  for  pollination.  If  the  stamens  mature  first,  the  pollen 
will  have  fallen  before  the  stigma  is  in  a  receptive  condition ; 
if  the  stigma  matures  first,  it  usually  will  have  been  pollinated 
by  pollen  from  other  flowers  before  the  stamens  in  the  same 
flower  have  shed  their  pollen.  Obviously,  in  either  case  effec- 
tive self-pollination  will  be  impossible  or  highly  improbable. 

Examine  all  the  flowers  available  and  list  them  below,  indi- 
cating, by  check  mark  in  the  proper  column,  to  which  of  the 
three  classes  they  belong: 


NAME 

STAMENS 
MATURE  FIRST 

STIGMA 
MATURES  FIRST 

BOTH  MATURE  AT 
SAME  TIME 

• 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  131,  132. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  152,  153. 
LUBBOCK.    Flowers,  Fruits,   and  Leaves,  chap.  ii.     The  Macmillan 
Company. 

[62] 


EXERCISE  50 


PREVENTION  OF  LOSS  OF  POLLEN 
Materials.    Flowers,  in  the  field  or  garden. 

Directions  for  work.  1.  Protection  from  rain.  Pollen  grains 
which  are  placed  in  water  soon  absorb  enough  water  to  cause 
them  to  burst.  Rain  may  either  destroy  the  pollen  or  wash  it 
out  of  the  flower.  Some  plants,  but  not  all,  have  flowers  so 
constructed  that  the  pollen  is  not  exposed  to  rain,  or  the  flowers 
may  close  in  rainy  or  cloudy  weather, 

List  the  kinds  studied,  and  in  column  ^  note  the  sort  of  pro- 
tection from  rain  which  you  find,  or  the  absence  of  protection. 

2.  Protection  from  injurious  insects.  Many  flowers  are  equipped 
with  devices  which  exclude  such  insects  as  might  feed  upon  the 
pollen  or  nectar  but  are  not  likely  to  cross-pollinate  the  flower. 
Ants  are  the  most  important  insects  in  this  class. 

The  most  common  protective  characters  are  hairs  on  the  stem 
or  flower  stalk,  sticky  zones  on  the  stems  or  flowers,  narrow 
corolla  tubes,  narrow-throated  corollas,  and  inclosure  of  the 
stamens  by  an  almost  closed  corolla.  Examine  the  flowers  you 
have  at  hand  and  note  the  protective  devices,  if  any,  in  column  B. 


NAME 


Reference 

LUBBOCK.    Flowers,  Fruits,  and   Leaves,  chap.  ii.     The  Macmillan 
Company. 

[63] 


EXERCISE  51 
CAN  POLLEN  BE  DISTRIBUTED  BY  WIND? 

Materials.  Any  of  the  following  which  may  be  in  flower  at  the 
proper  season :  cornstalks  in  tassel ;  pine  trees  or  cedar  trees  with 
staminate  cones ;  maple,  box  elder,  willow,  poplar,  or  ash  trees  in 
blossom ;  timothy  or  other  grasses  in  flower ;  ragweeds. 

Directions  for  work.  Select  for  study  several  species  if  pos- 
sible. Examine  the  flowers  to  identify  stamens  and  pistils.  In 
many  species  the  stamens  and  pistils  do  not  occur  in  the  same 
flower,,  and  often  not  on  the  same  individual.  What  relation 
does  this  have  to  the  'prevention  of  self-pollination  ? 

Note  the  character  of  the  pollen  and  its  abundance.  Is  it 
moist  and  sticky  or  dry  and  powdery?  Is  it  of  such  character 
as  to  be  readily  carried  by  the  wind?  Jar  a  flower-bearing 
branch  on  which  you  have  discovered  ripe  anthers.  Does  the 
pollen  fall  from  the  flowers,  and  is  it  carried  away  by  the  wind  ? 

Do  the  pistils  appear  to  be  well  adapted  to  catch  flying 
pollen  ?  It  is  suggested  that  pistils  which  extend  beyond  the 
calyx  and  corolla,  if  these  are  present,  and  pistils  which  have 
long  or  feathery  stigmas  would  be  more  likely  to  intercept 
flying  pollen  than  pistils  of  the  usual  sort. 

Is  this  method  of  pollination  economical  or  wasteful  of  pollen  ? 
Is  the  pollen  abundant  or  scanty  in  amount  in  the  plants  studied? 

Sum  up  your  entire  study  in  a  brief  statement  of  what  it 
has  shown  you  about  the  possibilities  of  wind  pollination.  Com- 
pare the  wind-pollinated  plants  and  tell  what  features  you  find 
common  to  most  of  them.  In  what  respects  are  their  flowers 
commonly  different  from  those  of  the  insect-pollinated  plants  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  p.  120. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  p.  143. 


[64] 


EXERCISE  52 

ADVANTAGES  FROM  DISPERSAL  OF  SEEDS 
Materials.    Dandelions  in  seed. 

Directions  for  work.  To  appreciate  the  advantages  resulting 
from  dispersal  of  seeds,  study  the  conditions  that  would  result 
if  seeds  were  not  dispersed.  Count  the  seedlike  fruits  on  a 
dandelion  head  or  make  a  close  estimate  of  the  number.  There 
is  one  seed  in  each  fruit.  What  is  the  total  number  of  seeds 
on  a  head?  Estimating  on  the  basis  of  the  number  of  heads 
produced  by  the  plant  you  are  examining,  as  shown  by  old 
seed  stalks,  flower  heads,  buds,  etc.,  what  is  the  approximate 
number  of  seeds  produced  per  dandelion  plant  ?  If  these  seeds 
were  to  fall  from  the  plant  without  being  scattered  about  by 
the  wind,  it  may  be  supposed  that  they  would  fall  within  an 
area  of  about  one  square  foot.  Supposing  them  to  be  evenly 
distributed  throughout  this  area,  how  many  seeds  would  there 
be  per  square  inch  ?  How  many  dandelion  plants  would  there 
be  room  for  in  this  area  providing  no  other  plants  occupied 
it  ?  How  many  square  inches  of  the  square  foot  are  actually 
unoccupied  by  the  parent  dandelion  and  other  perennial  plants  ? 
Do  you  consider  that  there  would  be  fair  opportunity  for 
any  considerable  number  of  new  dandelion  plants  to  establish 
themselves  under  the  conditions  supposed  above? 

Now  watch  dandelion  seeds  when  a  strong  wind  is  blowing. 
How  can  you  prove  that  seeds  are  carried  ?  Examine  the  area 
within  a  distance  of  one  or  two  hundred  feet  of  a  patch  of 
dandelions.  How  much  area  do  you  find  not  occupied  by  dan- 
delions ?  How  much  area  do  you  find  not  occupied  by  any 
perennial  plants?  How  many  dandelions  might  find  room 
within  the  area  over  which  seeds  are  known  to  be  distributed 
from  the  one  patch? 

State  your  opinion  regarding  the  advantage  of  dispersal  as 
shown  by  the  facts  learned  in  this  study. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  146-151. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  166-170. 

[65] 


EXERCISE  53 

WHAT  ADVANTAGES  ARE  POSSESSED  BY  PLANTS  HAVING 
WINGED  SEEDS  OR  FRUITS? 

Materials.  Winged  seeds  or  fruits.  Those  of  the  maple,  tree-of- 
heaven  (ailanthus),  hop  tree,  box  elder,  and  trumpet  creeper  are 
good.  Secure  as  many  kinds  as  possible. 

Directions  for  work.  Study  the  form  and  structure  of  the 
wing  and  its  effect  upon  dispersal  of  seeds. 

1.  Action  of  wing.  In  the  quiet  air  of  the  room  drop  several 
seed's  from  as  great  a  height  as  you  can  reach,  and  watch  them 
descend.  Do  they  "  fly  away  "  ?  That  is,  do  the  wings  cause  the 
seeds  to  travel  to  distant  parts  of  the  room,  or  do  the  seeds  alight 
on  the  floor  at  a  point  almost  directly  below  the  point  from 
which  they  started?  If  the  seeds  descend  directly,  instead  of 
flying  away,  what  is  the  effect  of  the  wings  upon  the  movement 
of  the  seeds. 

Estimate  the  effect  of  the  wings  in  the  following  manner. 
Experiment  with  the  seeds  until  you  have  found  at  least  a 
half  dozen  that  descend  at  approximately  the  same  speed.  Then 
remove  the  wings  from  one  half  of  the  seeds  in  the  lot.  Time  the 
fall  of  seeds  with  and  without  wings,  as  suggested  below: 

Let  one  of  the  pupils  ascend  a  step  ladder  or  stand  on  a 
table  so  as  to  be  able  to  drop  the  seeds  from  a  point  near  the 
ceiling.  Both  the  wingless  seeds  and  the  perfect  ones  should 
be  placed  on  the  palm  of  the  open  hand,  and  all  can  be  dropped 
simultaneously  by  turning  the  hand  palm  downward.  Let 
another  pupil  count  aloud  at  about  the  rate  of  a  clock's  ticking. 
This  can  be  best  arranged  by  having  a  small  clock  in  the  room 
and  actually  counting  the  ticks.  Let  one  pupil  begin  counting 
clock  ticks  while  the  other  drops  the  seeds  at  a  prearranged 
signal,  as,  for  example,  the  fifth  count.  The  remainder  of  the 
pupils  should  note  the  count  at  which  the  seeds  start,  the  count  at 
which  the  wingless  seeds  reach  the  floor,  and  the  count  at  which 
the  uninjured  seeds  reach  the  floor.  Which  lot  of  seeds  descends 
more  slowly  ?  How  much  more  slowly  ?  What  is  the  real  effect 
of  the  wing  ?  Is  the  wing  of  any  advantage,  so  far  as  dispersal 

[66] 


EXERCISE  53  (Continued) 

is  concerned,  in  quiet  air  ?  Is  the  wing  of  any  advantage,  and,  if 
so,  what  advantage,  when  the  wind  is  blowing  ? 

Try  the  above  experiments  with  several  kinds  of  seeds  to  see 
whether  your  conclusions  are  true  of  all.  Compare  several  kinds 
by  dropping  simultaneously.  On  the  basis  of  your  experiments, 
what  do  you  conclude  to  be  the  advantage  of  the  possession  of 
a  wing,  and  which  of  the  seeds  studied  is  best  equipped  in  this 
particular?  Test  your  conclusions  by  observing  seeds  falling 
from  trees  if  possible. 

2.  /Structure  of  wing.  Examine  and  describe  the  wings.  Note 
shape,  thickness,  width,  length,  and  relative  weight.  Can  you 
discover  anything  in  the  form  and  structure  of  different  wings 
that  accounts  for  the  peculiarities  of  their  action  ? 

Write  a  description  of  the  several  winged  seeds  and  fruits 
and  illustrate  with  drawings  which  show  the  important  features. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  146-155. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  166-171. 


[67] 


EXERCISE  54 

WHAT  ADVANTAGES  ARE  POSSESSED  BY  PLANTS  HAVING 
PLUMED  SEEDS  OR  FRUITS? 

Materials.  Plumed  seeds  of  several  sorts.  The  several  kinds  of 
milkweed,  dandelion,  goldenrod,  and  thistle  are  good. 

Directions  for  work.  Experiment  with  the  seeds  in  the  quiet 
air  of  the  classroom,  as  directed  for  winged  seeds.  Measure  the 
difference  in  rate  of  descent  for  seeds  with  the  plume  and  those 
from  which  the  plume  has  been  removed.  Also  allow  some  of 
the  seeds  to  descend  in  the  vicinity  of  an  open  window  through 
which  the  wind  is  blowing,  and  note  the  results. 

Compare  plumed  and  winged  seeds  with  each  other  by  drop- 
ping both  at  the  same  time  from  as  high  .a  position  as  possible, 
noting  relative  rate  of  descent. 

Which  kind  of  plumed  seed,  among  those  you  have  tried, 
appears  to  have  the  better  equipment  for  wide  dispersal?  In 
comparing  winged  and  plumed  seeds,  which  did  you  find  gener- 
ally superior  with  reference  to  dispersal?  Would  this  neces- 
sarily be  true  of  all  winged  and  plumed  seeds  ? 

Would  the  height  of  the  plant  on  which  the  seeds  were 
produced  be  important  in  connection  with  dispersal  ?  Would 
wings  and  plumes  be  equally  efficient  in  the  case  of  low  plants, 
such  as  the  dandelion  or  the  thistle  ? 

Illustrate  your  notes  with  sketches  of  several  different  types 
of  plumes. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  146-155. 
BERGEN  and  CALDWELL.  Introduction  to  Botany,  pp.  166-171. 


[68] 


EXERCISE  55 
WHAT   ADVANTAGE    IN    POSSESSING   BURS   OR    STICKERS? 

Materials.  Cockleburs  and  beggar-ticks  or  Spanish  needle ;  any 
other  kinds  of  "  stickers  "  ;  spring  balance  graduated  in  grams. 

Directions  for  work.  1.  Oocklebur.  Put  one  of  the  burs  against 
your  sleeve  and  notice  how  readily  it  takes  hold.  Pull  it  off, 
noting  how  strongly  it  holds  on.  By  what  means  does  it  hold 
so  firmly  ?  Examine  the  projections  with  which  the  surface  of 
the  bur  is  thickly  studded.  Are  they  simple  straight  spines, 
like  pins,  as  they  at  first  seem  ?  What  peculiarity  of  their 
shape  enables  them  to  hold  ?  To  measure  the  strength  of  one 
of  these  spines,  attach  a  thread  or  light  cord  to  the  spring 
balance  and  tie  a  loop  in  the  free  end  of  the  thread.  Hook  one 
of  the  spines  into  this  loop  and  pull  on  the  spring  balance  until 
the  spine  breaks  or  lets  go  of  the  thread.  What  was  the  maxi- 
mum amount  registered  by  the  balance  before  the  spine  failed? 
Repeat  with  several  other  spines.  What  is  the  average  strength 
with  which  the  spines  are  able  to  hold  fast? 

2.  Beggar-ticks.     Thrust  the  points  of  the  beggar-tick  into 
the  cloth  of  a  garment,   noting  the  relative  amount  of  force 
needed  to  insert  the  points  and  to  withdraw  them.    Do  they 
seem  to  hold  effectively  ?    Examine  the  spines  of  an  uninjured 
beggar-tick  with   a  magnifier  to  find  out  what  peculiarity  of 
structure  enables  it  to  hold  fast.    It  is  sometimes  noted  that 
after  beggar- ticks  have  been  adhering  to  the  clothing  for  some 
time  the  points  come  through  on  the  inside,  though  they  appar- 
ently did  npt  do  so  at  first.    Can  you  find  anything  in  their 
structure  that  would  favor  a  gradually  deeper  penetration  ? 

3.  Comparison  with  other  burs.    Make  a  rapid  study  of  other 
burs  which  are  available,  noting  resemblance  to  the  two  types 
studied  above  and  apparent  effectiveness  of  their  equipment. 

4.  Comparison  with  other  seeds.    Burs  commonly  become  en- 
tangled in  the  coats  of  grazing  animals  in  the  autumn.    How 
long  would  they  probably  remain  attached  to  the  animal?    In 
the  case  of  domestic  animals,  how  far  might  it  reasonably  be 
supposed  that  they  might  be  carried  in  the  interval  ?    How  far 

[69] 


EXERCISE  55  (Continued) 

might  burs  have  been  carried  in  former  times  by  such  animals 
as  the  deer  and  buffalo  ? 

Compare  wind-carried  seeds  and  animal-carried  seeds  of  the 
type  of  the  burs  with  regard  to  the  following  points: 

1.  Which  sort  of  equipment  is  more  sure  to  secure  the  dis- 
persal of  almost  all  the  seeds  on  the  plant  ? 

2.  Which  sort  of  equipment  is  likely  to  secure  the  carrying 
of  at  least  a  few  seeds  to  the  greatest  distance  ? 

How   do  you  account  for  the   fact  that  strange  weeds  are 
often  found  in  the  vicinity  of  wool-cleaning  establishments  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  146-155. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  166-171. 


[70] 


EXERCISE  56 
DISPERSAL  OF  SEEDS  OF  FLESHY  FRUITS 

Materials.  Fleshy,  edible  fruits  of  several  kipds,  such  as  apple, 
pear,  raspberry,  strawberry,  mulberry,  and  many  fruits  of  wild 
plants. 

Directions  for  work.  Seeds  of  fleshy  fruits  are  commonly  dis- 
tributed by  being  eaten  along  with  the  pulp  and  later  voided 
uninjured  from  the  body  of  the  animal.  Birds  are  particularly 
notable  as  distributors  of  seeds  in  this  manner. 

What  are  the  features  of  the  fruits  you  are  studying  which 
might  attract  the  attention  of  animals  and  cause  them  to  eat 
the  fruit?  Note  color,  odor,  and  flavor. 

What  characteristics,  such  as  small  size  of  the  seeds  and 
intimate  relation  to  pulp,  make  it  extremely  probable  that  the 
seeds  will  be  swallowed  along  with  the  pulp  ?  . 

What  characteristics  of  the  seeds  make  it  appear  improb- 
able that  any  large  proportion  will  be  destroyed  by  mastication, 
by  grinding  in  the  gizzards  of  birds,  or  by  the  action  of  the 
digestive  juices  ? 

Make  observations  in  the  field  to  determine  which  fruits  are 
readily  eaten  by  birds.  Find  out  also  whether  any  plants  of 
these  sorts  may  be  found  growing  in  places  where  their  presence 
is  difficult  to  explain  except  on  the  supposition  that  seeds  are 
carried  by  birds.  Look  especially  for  plants  growing  in  the 
forks  of  trees  or  in  knotholes,  on  thatched  roofs  and  on  old 
stacks  of  decaying  straw  or  hay,  and  along  fences  or  other 
places  where  birds  are  accustomed  to  perch. 

From  your  observation,  do  you  find  that  this  is  a  successful 
means  of  dispersal  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  146-155. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  166-171. 


[71] 


EXERCISE  57 
PRODUCTION  OF  A  PLANT  FROM  A  SEED 

Materials.  Unroasted  peanuts  ;  three-inch  paraffined  paper  plant 
pots;  clean  sawdust  or  sand. 

Directions  for  work.  Let  each  pupil  fill  one  of  the  pots  with 
sawdust  or  sand  which  has  been  thoroughly  wet.  Plant  sev- 
eral seeds  in  each  one,  and  label  the  pot  for  proper  identi- 
fication. Set  the  po'ts  aside  in  a  dark  place  until  the  young 
plants  begin  to  appear  above  the  surface  of  the  ground.  Plant 
other  seeds  at  intervals  during  the  progress  of  the  experiment 
in  order  to  assure  having  a  few  plants  in  early  stages  for  com- 
parison at  all  times.  Keep  a  record  of  the  growth  of  the  young 
plants  by  making  drawings  daily,  or  at  shorter  intervals  if 
growth  is  rapid.  When  the  young  plants  are  erect  and  the 
first  pair,  of  foliage  leaves  are  well  grown,  dig  up  several  of 
them  and  make  a  drawing  showing  all  parts,  including  the 
roots.  Carefully  label  all  the  parts  of  the  young  plant,  using 
the  textbook  to  ascertain  the  proper  names. 

Dig  up  some  of  the  seeds  that  were  planted  later  in  order  to 
secure  stages  in  the  development  of  the  plants  before  they  have 
come  up.  Complete  your  series  of  sketches.  Using  your  draw- 
ings as  memoranda,  write  a  connected  story  of  the  development 
of  a  young  plant  from  a  seed. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  136-145. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  156-166. 


[72] 


EXERCISE  58 
STRUCTURE  OF  A  SEED 

Materials.  Seeds  of  bean  or  peanut;  blotting  paper  or  filter 
paper ;  dish  with  cover. 

Directions  for  work.  Soak  some  seeds  in  water  for  twenty- 
four  hours.  Remove  the  seed  coatings  from  the  seeds  and 
attempt  to  find  in  the  seeds  the  parts  that  were  recognized  in 
the  seedling  plant.  Do  you  find  the  cotyledons  ?  Describe  them. 
Look  for  the  hypocotyl ;  for  the  plumule.  Examine  the  plumule 
with  a  magnifier  or  with  the  low  power  of  the  microscope  to 
determine  whether  the  first  pair  of  leaves  is  already  present  in 
the  plumule. 

When  you  have  satisfied  yourself  that  you  have  identified  in 
the  seed  the  part  from  which  each  of  the  organs  of  the  young 
plant  develops,  make  a  diagram  representing  an  ideal  vertical 
section  through  the  seed  from  end  to  end,  showing  the  hypocotyl, 
plumule,  and  cotyledons  in  proper  relation  to  each  other. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  136-137. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.- 156—160. 


[73] 


EXERCISE  59 
COMPARISON  OF  SEEDS  AND  SEEDLINGS 

Materials.  Seeds  and  seedlings  of  as  many  as  possible  of  the 
following,  and  any  other  seedlings  that  may  be  readily  secured  : 
pea ;  castor  bean ;  pumpkin  or  winter  squash. 

Directions  for  work.  Compare  these  seeds  and  seedlings  with 
each  other  and  with  the  bean  or  peanut,  noting  differences. 

The  principal  differences  noted  will  be  that  the  pea  cotyledons 
are  not  raised  above  the  ground ;  the  cotyledons  of  the  castor 
bean  are  not  stored  with  food  materials  and  become  effective 
working  leaves ;  and  in  the  pumpkin,  though  the  food  is  stored 
in  the  cotyledons,  they  become  large  and  remain  long  on  the 
plant,  while  the  plumule  is  very  slow  in  developing. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  141-142. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  164. 


EXERCISE  60 
THE  COTYLEDONS 

Materials.  Young  plants  and  seeds  as  used  in  the  preceding 
exercise,  in  various  stages  of  growth;  iodine  solution. 

Directions  for  work.  It  will  be  found  that  it  is  frequently 
stated  that  the  cotyledons  are  in  fact  leaves.  What  facts  can 
you  discover  that  appear  to  confirm  or  to  dispute  this  state- 
ment? Study  several  kinds  of  seedlings.  Do  the  cotyledons 
have  either  of  the  types  of  arrangement  that  you  have  found 
to  be  characteristic  of  the  arrangements  of  leaves  on  a  stem  ? 
Are  there  buds  in  the  positions  where  you  should  expect  to 
find  buds  if  the  cotyledons  are  in  reality  leaves  ?  Do  the  coty- 
ledons of  any  plants  studied  perform  the  work  of  leaves  ? 

What  special  work  do  cotyledons,  or  at  least  some  of  them, 
perform  that  is  different  from  the  usual  work  of  leaves?  Ex- 
amine a  series  of  cotyledons  from  a  bean  or  a  peanut  plant. 
Note  any  changes  in  the  plumpness  and  apparent  volume  of  the 
cotyledons  as  they  grow  older.  Break  open  the  cotyledons  and 
test  the  interiors  for  starch.  What  differences  in  this  particular 
do  you  find  between  older  and  younger  cotyledons?  If  you 
can  find  some  plants  that  are  old  enough  so  that  the  cotyledons 
are  about  to  fall  off,  include  them  in  the  test,  or  let  some  of 
the  plants  grow  and  watch  the  fate  of  the  cotyledons.  What 
does  your  study  indicate  as  to  the  office  which  the  cotyledons 
are  performing? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  142-144. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  158-165. 


[75] 


EXERCISE  61 
A  MONOCOTYLEDONOUS  SEED 

Materials.  Seeds  of  corn  which  have  been  soaked  for  at  least 
twenty-four  hours,  and  some  which  have  been  germinated  on 
blotting  paper. 

Directions  for  work.  Examine  the  germinated  seeds  to  iden- 
tify the  plumule  and  the  hypocotyl  and  root.  Examine  one  of 
the  soaked  seeds,  and  by  comparison  with  the  germinated  seed 
locate  the  general  position  of  the  plumule  and  the  hypocotyl. 
Then  cut  the  seed  in  two  lengthwise  through  the  center  so  as 
to  split  the  young  plant  (embryo)  from  end  to  end.  This  can 
best  be  done  by  making  the  first  cut  a  little  to  one  side  of  the 
center  and  then  carefully  shaving  off  the  cut  surface  until  the 
growing  points  are  properly  exposed.  By  the  aid  of  illustrations 
identify  the  cotyledon  ("Practical  Botany,"  Figs.  128,  129). 

In  this  case  does  the  cotyledon  come  aboveground.  ?  Is  the 
food  stored  in  the  cotyledon  or  outside  of  it  ?  What  office  does 
the  cotyledon  serve  ? 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  p.  137,  Figs.  127-129. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  158,  Fig.  143. 


[76] 


EXERCISE  62 

WHAT  IS  THE  EFFECT  OF  DIFFERENT  TEMPERATURES 
ON   GERMINATION? 

Materials.  Pea  seeds ;  filter  or  blotting  paper ;  dishes  with 
covers. 

Directions  for  work.  Soak  all  the  seeds  for  twenty-four  hours. 
Divide  the  seeds  into  four  or  five  lots  and  place  each  lot  on 
wet  filter  paper  or  blotting  paper  in  a  covered  dish.  Do  not 
use  more  seeds  than  will  lie  on  the  bottom  of  the  dish  without 
crowding.  Put  one  of  the  dishes  in  the  coolest  place  available 
but  not  where  the  seeds  will  freeze.  Put  another  dish  in  the 
warmest  place  available  but  not  where  the  temperature  will 
rise  to  the  boiling  point.  For  the  other  dishes  select  places  at 
intermediate  temperatures.  It  is  desirable  that  the  temperatures 
at  the  various  situations  be  as  constant  as  possible,  and  the 
average  at  each  place  should  be  obtained  with  a  thermometer. 
However,  if  it  is  not  possible  to  secure  uniform  temperatures, 
the  results  will  be  instructive,  though  not  so  exact.  If  it  is 
found  that  there  is  considerable  variation  of  temperature,  it 
may  be  better  to  plant  all  of  the  seeds  in  sand  or  sawdust, 
since  the  temperature  in  these  substances  will  vary  less  than 
in  the  air.  A  thermometer  inserted  in  the  soil  among  the  seeds 
will  give  the  temperature,  and  readings  may  be  taken  several 
times  each  day. 

If  the  seeds  are  placed  in  dishes  it  will  be  well  to  darken 
them,  since  no  doubt  at  least  some  of  the  seeds  will  be  placed 
in  a  dark  place  and  the  results  will  be  fairly  comparable  only 
if  all  are  equally  darkened. 

At  the  end  of  four  or  five  days  examine  each  lot  of  seeds  and 
note  how  many  are  sprouted,  how  many  have  not  germinated, 
the  relative  length  of  the  sprouts,  and  the  general  appearance 
of  the  seedlings.  Record  the  observations  in  the  table  on  page  78 
and  write  a  full  description  of  your  experiment,  giving  all 
details  that  might  in  any  way  affect  the  results.  What  are 
your  conclusions  about  the  effect  of  different  temperatures 
within  the  range  of  temperatures  used? 

[77] 


EXERCISE  62  (Continued) 


NUMBER  OF 
SEEDS 

NUMBER 
GERMINATED 

PER  CENT 
GERMINATED 

AMOUNT  OF  GROWTH 
AND  GENERAL 
CONDITION 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  139,  140. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  161. 


[78] 


EXERCISE  63 

WHAT  IS  THE  EFFECT  OF  GRAVITY  ON  THE  GROWTH  OF 
ROOT  AND  STEM? 

Materials.  Pea  seedlings  an  inch  in  length ;  sawdust ;  drinking- 
glass  with  sloping  sides. 

Directions  for  work.  Place  the  seedlings  in  the  drinking-glass 
in  various  positions,  so  that  some  of  them  have  root  and  stem 
horizontal,  others  have  the  stem  downward  and  the  root  tip  up- 
ward, and  others  are  in  various  oblique  positions.  Place  them 
against  the  glass  and  pack  wet  sawdust  in  the  glass  so  as  to  hold 
them  in  position  and  keep  them  moist.  Place  the  experiment 
in  the  dark.  Observe  later  in  the  day  and  for  several  successive 
days,  making  observations  through  the  glass.  Later,  when  the 
roots  and  stems  have  made  considerable  growth,  the  plants  may 
be  removed  from  the  sawdust  for  more  exact  study.  What 
direction  have  the  root  tips  taken  ?  Has  the  direction  been 
influenced  by  the  position  in  which  you  placed  the  plants  ? 
How  has  the  stem  reacted  in  this  experiment  ?  What  reasons 
do  you  have  for  believing  that  it  is  gravity  which  controls  the 
direction  of  growth  ? 

It  is  possible  to  secure  boxes  with  glass  sides,  made  especially 
for  this  experiment,  and  they  are  very  satisfactory.  It  may  also 
be  performed,  if  the  materials  are  at  hand,  in  the  following 
manner :  Wrap  a  piece  of  sheet  cork  about  three  by  six  inches 
in  size  with  blotting  paper.  Pin  the  seedlings  in  contact  with 
it  in  the  positions  desired  and  stand  the  cork  upright  with  the 
lower  end  of  the  blotting  paper  in  water.  Cover  the  whole  to 
prevent  evaporation  and  to  exclude  light. 


[79] 


EXERCISE  64 
HOW  DO  STEMS  AND  LEAVES  REACT  TO  LIGHT? 

Materials.  Seedlings  of  pea,  bean,  peanut,  or  any  other  seedlings 
available.  Older  plants  may  also  be  used. 

Directions  for  work.  Place  the  seedlings  in  a  small  box  which 
is  tight  enough  to  exclude  light  except  for  a  small  opening  on 
one  side  at  about  the  level  of  the  leaves  of  the  seedlings  'to 
be  used.  Note  the  position  of  the  stem  and  principal  leaves  of 
the  plants  and  make  a  memorandum  of  the  facts.  Place  the 
inclosing  box  as  near  to  the  window  as  possible,  with  the  open- 
ing toward  the  window. 

Make  daily  observations  on  the  plant  for  several  days,  noting 
any  change  of  position  of  the  leaves  and  stem  with  relation  to 
the  light.  What  position  does  the  stem  assume  with  relation  to 
the  direction  of  incoming  light?  Is  this  equally  true  of  the 
older  parts  of  the  stem  as  well  as  of  the  newer  parts?  What 
position  do  the  leaves  assume  with  reference  to  the  light  which 
reaches  them  ?  Is  there  any  difference  in  the  action  of  old  and 
young  leaves  ? 

Reverse  the  position  of  the  plant;  that  is,  rotate  it  through 
180  degrees,  so  that  the  side  which  was  formerly  toward  the 
light  is  turned  away  from  it  but  the  plant  remains  standing  at 
the  same  place.  How  do  leaf  and  stem  react  at  this  time  ? 

Is  the  position  assumed  by  the  leaves  such  as  secures  the 
best  exposure  to  the  light  entering  the  opening? 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  56,  57,  64,  65. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  72-76. 


[80] 


EXERCISE  65 
RESPONSE  TO  TOUCH 

Materials.  Small  plants  of  the  sort  known  as  "  sensitive  plants  " 
(Mimosa  pudica).  These  are  often  kept  in  homes  and  conservatories 
as  curiosities.  They  may  be  readily  grown  from  seed. 

Directions  for  work.  The  plant  will  react  most  satisfactorily 
when  standing  in  good  light.  It  should  be  placed  in  a  window 
some  time  before  it  is  to  be  used,  in  order  that  it  may  have 
time  to  recover  from  the  disturbance  occasioned  by  moving  it, 
and  it  is  well  to  cover  it  with  a  glass  bell  jar  to  protect  it 
from  accidental  disturbance  before  time  for  the  experiment. 

Tap  one  of  the  leaflets  lightly  with  a  pencil.  What  action 
follows  ?  Repeat  the  tap,  but  somewhat  more  vigorously.  Is 
the  reaction  in  any  degree  proportioned  to  the  strength  of  the 
stimulus  ? 

Pinch  a  terminal  leaflet  on  one  of  the  leaves  with  the  forceps 
or  the  finger  nails,  using  care  not  to  shake  the  entire  leaf. 
Does  the  stimulus  instantaneously  affect  the  whole  leaf,  or  is  it 
propagated  from  the  place  first  affected  to  other  parts  of  the 
leaf  ?  What  evidence  do  you  have  upon  which  you  base  your 
conclusion?  Describe  in  detail  what  happens  in  this  experiment, 
including  the  time  intervals  concerned,  repeating  the  trial  with 
another  leaf,  if  necessary,  to  secure  data. 

Do  the  leaves  recover  their  original  condition  after  a  period 
of  rest  ?  About  how  long  does  recovery  require  ?  Are  they 
able  to  respond  again  after  recovery  ?  Is  the  second  response 
apparently  equal  to  and  like  the  first  response  ? 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  388-389. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  22. 


[81] 


EXERCISE  66 
RESPONSE  OF  TENDRILS 

Materials.  Pea  plants  with  tendrils,  or  other  tendril-bearing 
plants. 

Directions  for  work.  Select  vigorous  plants  in  apparent  good 
condition.  Stroke  a  tendril  gently  with  a  pencil,  being  careful 
that  it  shall  be  touched  only  on  one  side.  Repeat  with  several 
other  tendrils.  Make  careful  note  of  the  position  and  curvature 
of  the  tendril  and  observe  it  repeatedly  for  several  minutes, 
making  memorandum  of  the  time  and  the  curvature  of  the 
tendril  at  each  observation.  Does  the  stimulus  of  contact  pro- 
duce any  curvature  ?  If  so,  to  which  side  does  the  tendril 
curve,  and  is  this  curvature  permanent  ? 

Thrust  a  wire  or  other  slender  object  into  the  soil  and  bend 
it  so  that  it  is  in  contact  with  one  of  the  tendrils  near  its  tip. 
Allow  the  wire  to  remain  in  this  position,  so  that  in  this  case 
the  contact  with  the  tendril  is  permanent,  instead  of  temporary 
as  in  the  previous  trial.  Repeat  with  several  other  tendrils. 
Does  the  tendril  curve  ?  Is  the  curvature  permanent  ?  Does 
the  curvature  become  greater  in  amount  than  in  the  previous 
trial  ?  Does  the  tendril  finally  take  hold  of  the  object  as  you 
are  used  to  seeing  tendrils  attached  ? 

In  writing  your  notes  discuss  both  parts  of  the  exercise  and 
write  a  clear  account  of  how  a  tendril  takes  hold  of  a  support. 


References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  62-01. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  71,  75. 


[82] 


EXERCISE  67 
RESPIRATION 

Materials.  Small  potted  plant  or  germinating  seeds  ;  four  6-ounce, 
wide-mouthed  bottles  with  two-hole  rubber  stoppers ;  limewater ; 
caustic-soda  solution ;  respiration  chamber,  arranged  with  a  bell-jar 
and  air-pump  platform ;  filter  pump ;  glass  and  rubber  tubing. 
Assemble  apparatus  as  shown  in  the  illustration. 

Directions  for  work.  With  the  apparatus  assembled  as  illus- 
trated, place  the  plant  or  seeds  in  the  respiration  chamber  (4) 
and  some  caustic- 
soda  solution  in  the 
first  and  second  bot- 
ties  (land  2).  Close 
all  bottles  and  the 
respiration  chamber 
tightly  and  start  the 
filter  pump.  If  air 
does  not  bubble  through  the  soda  solutions,  there  must  be  leaks 
in  some  of  the  connections.  Go  over  the  whole  train  and  tighten 
up  all  parts  until  air  comes  through  steadily,  as  indicated  by  the 
bubbles  in  the  bottles.  Wire  the  joints  between  rubber  and 
glass  tubing  if  necessary. 

After  air  has  been  flowing  steadily  for  several  minutes  place 
limewater  in  bottles  3  and  5.  Make  sure  again  that  the  air 
passes  through  the  whole  train  of  bottles.  If  a  green  plant  is 
used,  darken  the  chamber  containing  it  in  order  to  prevent 
photosynthesis,  else  the  results  of  respiration  and  photosynthesis 
may  not  be  distinguishable.  Bottles  1  and  2  should  remove  the 
carbon  dioxide  from  the  incoming  air,  and  bottle  3  show  whether 
this  has  been  accomplished ;  bottle  5  will  show  whether  there 
is  any  carbon  dioxide  in  the  outgoing  air. 

Does  a  plant  give  off  carbon  dioxide  ? 

References 

BKKGEN  and  CALDWELL.    Practical  Botany,  pp.  19,  76. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  46-47. 


[83] 


EXERCISE  68 

HOW  MUCH  FORCE  DOES  THE  WIND  EXERT 
AGAINST  A  TREE? 

Materials.  A  small  tree  one  or  two  inches  in  diameter  near  the 
ground ;  ax ;  rope ;  heavy  spring  balance.  Select  a  tree  which  is 
not  valuable,  as  it  will  be  destroyed  by  the  experiment. 

Directions  for  work.  On  a  windy  day  cut  the  trunk  nearly 
through  close  to  the  ground,  beginning  on  the  side  toward 
the  wind,  so  that  the  remaining  bark  and  wood  will  act  as  a 
hinge.  Do  not  allow  the  tree  to  fall.  Tie  a  rope  to  the  trunk 
as  near  the  center  of  the  crown  as  possible.  Attach  a  spring 
balance  to  the  rope  and  support  the  tree  against  the  force  of  the 
wind  by  pulling  on  the-  spring  balance.  It  will  be  necessary  for 
someone  to  steady  the  tree  at  the  same  time  so  that  it  cannot 
fall  laterally. 

How  many  pounds  force  does  the  wind  exert,  tending  to  over- 
throw the  tree  ?  How  was  this  force  resisted  by  the  uninjured 
tree  ?  Attach  the  spring  balance  to  the  trunk  one  or  two  feet 
above  the  ground  and  note  the  pull  necessary  to  keep  the  tree 
in  an  upright  position.  How  great  strain  does  the  trunk  sus- 
tain at  this  point? 

Based  on  your  experiment,  estimate  the  pressure  of  the  wind 
against  any  large  tree  in  the  vicinity,  supposing  the  wind  to 
have  the  same  velocity  as  it  had  at  the  time  of  the  experiment. 
This  estimate  will  necessarily  be  only  a  very  rough  approxi- 
mation, but  it  should  give  you  some  idea  of  the  stress  to  which 
large  trees  are  subject  in  time  of  storm. 


[84] 


EXERCISE  69 


DOES  THE  BARK  ASSIST  IN  STRENGTHENING  THE   STEM? 

Materials.  A  dozen  straight  branches  of  willow,  or  other  available 
tree,  not  over  one-half  inch  in  diameter,  all  of  the  same  diameter 
and  as  nearly  alike  in  all  particulars  as  possible ;  small  bucket  and 
sand;  balances. 

Directions  for  work.  Select  eight  or  ten  of  the  branches  and 
divide  them  into  two  lots.  Peel  the  bark  from  one  lot,  but  do 
not  injure  the  remainder.  Support  one  of  the  sticks  across  two 
chairs  which  are  two  feet  apart.  Attach  the  bucket  to  the  stick 
midway  between  the  chairs  and  add  sand  until  the  stick  breaks 
or  gives  way  in  some  manner.  Weigh  the  bucket  and  sand  to 
determine  the  force  applied  at  instant  of  failure,  and  record  the 
weight  below.  Do  the  same  with  each  stick. 

What  is  the  average  breaking  force  for  those  with  bark  ? 
For  those  without  ?  Can  you  determine  by  examination  of  the 
broken  sticks  how  the  bark  gave  strength  ? 


BRANCHES  WITH  BARK,  BREAKING 
FORCE 

BRANCHES  WITHOUT  BARK,  BREAKING 
FORCE 

Average 

Average 

[85] 


EXERCISE  70 
TENSILE  STRENGTH  OF  BARK 

Materials.  Strips  of  bark  from  the  branches  peeled  in  the  pre- 
ceding exercise,  as  well  as  strips  of  fresh  bark  from  other  kinds  of 
trees. 

Directions  for  work.  Cut  the  bark  into  strips  of  uniform 
width.  Clamp  one  end  of  a  strip  in  a  vise  and  attach  a  spring 
balance  to  the  other  end  by  means  of  a  small  portable  vise,  as 
a  wooden  cabinet-maker's  clamp.  Pull  upon  the  spring  balance 
until  the  strip  of  bark  tears,  noting  the  reading  of  the  balance 
at  the  time  the  bark  gives  way.  Repeat  with  several  pieces  of 
bark  of  the  same  kind  in  order  to  get  an  average  result.  Secure 
similar  data  for  bark  from  other  species  of  trees. 

Does  the  tensile  strength  of  bark  appear  to  you  to  be  rela- 
tively great  ?  Is  there  any  marked  difference  in  bark  from 
various  kinds  of  plants  ?  Do  you  know  of  any  textile  or  cord- 
age fibers  that  are  secured  from  bark,  and,  if  so,  what  are  they  ? 
What  materials  are  manufactured  from  them? 

References 

,    BERGEN  and  CALDWELL.   Practical  Botany,  p.  47. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  p.  65. 


[86] 


EXERCISE  71 
COMPETITION  BETWEEN  BRANCHES,  AND  SELF-PRUNING 

Materials.  Several  groups  of  young  trees  growing  close  together. 
The  trees  should  be  from  ten  to  twenty-five  feet  high  and  must 
stand  close  enough  to  allow  the  tops  to  crowd  each  other  a  little. 

Directions  for  work.  Examine  the  group  of  trees  from  the 
outside.  It  will  doubtless  be  found  that  they  are  clothed  with' 
leafy  branches  almost  to  the  ground.  Enter  the  group  and  look 
for  the  living,  leafy  branches.  What  part  of  the  trunk  is  bear- 
ing living  branches  ?  Why  are  there  none  on  other  parts  of  the 
trunk  ?  Were  there  ever  branches  lower  down  ?  If  so,  what 
has  happened  to  them  ?  Do  the  dead  branches  remain  on  the 
tree  for  many  years  ?  Which  fall  earlier,  the  large  or  the  small 
branches  ?  By  studying  trees  in  different  situations  find  out 
whether  the  branches  die  while  smaller  on  trees  that  are  in 
crowded  situations  or  on  those  in  open  places,  and  which  of 
these  situations  favors  the  production  of  trees  with  straight, 
smooth  trunks.  Which  would  finally  be  most  suitable  for 
poles  and  lumber  ? 

Study  the  relation  of  branches  to  knots  in  the  wood.  If  it 
is  allowable  to  cut  down  one  of  the  trees,  do  so,  selecting  a 
tree  that  has  a  number  of  good-sized  dead  branches  or  branch 
stubs  and  some  living  branches.  Cut  sections  of  the  trunk  in- 
cluding such  branches  as  mentioned  above.  Take  the  pieces  to 
the  laboratory  and  split  or  saw  them  lengthwise  through  the 
branches.  Study  the  direction  of  the  wood  fibers  in  relation  to 
the  living  branch.  Try  to  imagine  how  the  grain  would  run 
in  a  plain-sawed  board  taken  from  such  a  part  of  the  tree,  and 
compare  with  knotty  lumber.  Would  the  boards  sawed  from  a 
tree  trunk  in  the  vicinity  of  the  base  of  a  living  branch  be 
straight-grained  or  cross-grained?  Would  any  knot  that  was 
found  in  such  a  board  be  a  loose  knot  or  a  solid  one  ?  In  like 
manner  examine  the  surface  split  through  a  dead  branch.  Note 
particularly  the  annual  layers  of  wood  in  the  vicinity  of  the 
dead  branch.  How  many  years  ago  did  the  branch  die  ?  Are 
the  layers  of  wood  formed  since  then  united  with  the  wood  of 

[87] 


EXERCISE  71  (Continued) 

the  branch  ?  If  this  branch  were  buried  deeply  by  the  farther 
growth  of  the  tree  and  boards  were  sawed  from  this  part  of 
the  trunk,  would  the  resultant  knots  be  loose  or  solid  ?  What, 
then,  is  the  origin  of  knotholes  in  boards  ? 

If  trees  are  planted  with  the  intention  of  producing  lumber, 
should  they  be  planted  close  together  or  far  apart  ?  What 
advantages  would  accrue,  in  the  amount  and  quality  of  the 
product,  by  the  method  you  suggest  ?  How  would  you  decide, 
in  looking  over  a  grove,  whether  the  trees  had  been  planted  at 
the  right  distance  apart? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  66,  67. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  77-79. 


[88] 


EXERCISE  72 
IN  WHAT  MANNER  ARE  WOUNDS  IN  TREES  HEALED? 

Materials.  Shade  and  orchard  trees"  with  dead  branches  and 
accidental  injuries. 

Directions  for  work.  Examine  shade  trees  or  neglected  fruit 
trees  on  which  branches  have  died  or  broken  and  note  the 
growth  of  adjacent  tissues  over  the  wound.  If  possible,  collect 
pieces  of  wood  showing  all  stages  in  the  closing  of  a  wound, 
from  the  early  condition,  such  as  is  represented  in  the  slight 
thickening  about  the  base  of  a  newly  killed  branch,  to  those 
cases  in  which  the  opening  is  completely  closed  on  the  outside. 
Split  these  pieces  through  the  healing  wound  and  describe  the 
process  by  which  the  wound  is  closed.  Selecting  a  wound  that 
appears  to  be  completely  healed,  note  the  original  diameter  of 
the  wound  and  the  number  of  years  required  to  close  it.  Note 
also  whether  the  wound  is  completely  healed  or  whether  there 
is  inclosed  within  it  any  partly  decayed  wood,  which  may  be 
infected  with  wood-rotting  fungi  and  thus  serve  as  a  source  of 
infection  for  the  heartwood  of  the  tree.  Do  large  or  small 
wounds  heal  the  more  perfectly  ? 

Examine  trees  from  which  large  branches  have  been  removed 
or  which  have  been  injured  by  the  removal  of  relatively  large 
areas  of  bark,  as  street  trees  which  have  been  gnawed  by  horses. 
Do  any  of  the  wounds  appear  to  be  too  large  to  be  repaired 
by  natural  processes  before  the  wood  of  the  trunk  has  seriously 
decayed  ?  So  far  as  you  can  determine  by  superficial  examina- 
tion, how  wide  an  area  may  be  successfully  healed  by  natural 
processes  ?  Would  painting  over  the  exposed  wood  with  disin- 
fectant substances  assist  in  any  way  ?  (Note  that  different 
kinds  of  trees  may  differ  widely  in  respect  to  ability  to- 
survive  injuries.) 

Visit  an  orchard  which  has  been  "  trimmed  "  within  the  last 
few  years.  Note  whether  the  cut  surfaces  are  being  healed 
without  decay.  If  possible,  find  cases  in  which  the  stub  has 
been  left  too  long,  thus  hindering  closure  of  the  wound,  and 
other  cases  in  which  it  has  been  cut  too  close  to  the  trunk,  thus 

[89] 


EXERCISE  72  (Continued) 

making  an  unnecessarily  large  wound.    Decide  upon  the  proper 
point  to  cut  a  branch  which  is  to  be  removed. 

If  there  are  trees  in  the  vicinity  which  have  been  treated  by 
a  skilled  tree  surgeon,  visit  them  and  study  both  his  methods 
and  the  evidences  of  their  success. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  p.  53. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  p.  105. 


[90] 


EXERCISE  73 

WHAT  PRECAUTIONS  ARE  NECESSARY  IN  TRANSPLANTING 
YOUNG  PLANTS? 

Materials.  A  tray  of  earth  with  seedlings  of  tomato,  cabbage,  or 
other  small  plants ;  a  second  tray  with  earth  to  which  seedlings 
may  be  transplanted.  Both  trays  must  have  holes  for  drainage. 

Directions  for  work.  Transplant  groups  of  seedlings  as  directed 
below,  using  great  care.  Young  seedlings  are  very  delicate. 

Group  A.  Lift  out  a  clump  of  dirt  containing  a  number  of 
seedlings.  Gently  loosen  the  dirt  from  the  roots  and  transfer 
each  plant  quickly  to  a  hole  in  the  earth  in  the  second  tray. 
These  holes  may  be  made  by  use  of  a  pointed  stick.  Press  the 
earth  firmly  about  the  roots.  Reject  all  small  or  weak  plants. 

G-roup  B.    Transplant  as  directed  for  Group  A. 

Group  C.  Handle  same  as  Group  A  with  the  exception  that 
the  roots  are  to  be  exposed  to  the  air  several  minutes.  Record 
the  time  of  exposure. 

Group  D.  Handle  same  as  Group  A  except  that  the  ground 
is  not  to  be  pressed  about  the  roots  more  than  necessary  to  keep 
the  plants  in  position. 

Group  E.  Transplant  carefully  in  all  respects,  but  bruise  the 
stem  of  each  plant  slightly  by  pinching  it. 

Group  F.  Allow  a  certain  number  of  plants  to  remain  in  the 
original  tray  undisturbed.  Water  them  and  care  for  them  just 
as  you  do  for  those  that  have  been  transplanted. 

Cover  all  plants  with  newspaper  except  Groups  B  and  F. 
Set  them  in  a  light  place  and  water  freely  for  several  days. 
The  newspaper  should  protect  those  which  are  covered  from 
excessive  transpiration.  After  several  days  the  paper  may  be 
removed.  At  the  end  of  a  week  compare  the  groups.  What  do 
you  learn  from  each  group  ? 

Write  careful  directions  for  transplanting,  emphasizing  the 
points  you  have  found  to  be  important. 

Watch  the  plants  for  several  weeks,  and  by  comparing  Group 
F  with  the  other  groups  try  to  determine  whether  transplanting 
is  necessarily  harmful  to  plants. 

[91] 


EXERCISE  74 
TRANSPLANTING  TREES  OR  SHRUBS 

Materials.  Small  trees,  not  over  six  feet  tall,  or  shrubs  of  any 
kind  available.  Materials  may  be  purchased,  but  it  is  as  well  to 
find  wild  trees  or  shrubs  that  may  be  dug  up  and  transplanted  to 
the  school  grounds.  The  work  should  be  done  in  the  spring  before 
the  buds  start. 

Directions  for  work.  Dig  up  the  shrubs  or  trees  with  care  to 
secure  rather  long,  uninjured  roots.  Are  you  able  to  secure  the 
whole  root  system  ?  Protect  the  roots  from  the  air  and  sun 
while  the  plants  are  taken  to  their  new  location. 

At  the  point  where  each  plant  is  to  be  placed  dig  a  hole  at 
least  two  feet  in  diameter  and  deep  enough  to  set  the  plant 
slightly  deeper  than  it  was  originally.  With  a  sharp  knife  trim 
off  any  broken  or  diseased  roots  and  set  the  plant  in  the  hole. 
Spread  out  the  roots  in  their  natural  position  and  let  one 
member  of  the  class  hold  the  plant  in  position  while  others 
fill  in  the  earth  about  the  roots.  Pack  the  earth  firmly. 

Prune  the  top  with  reference  to  (1)  the  form  which  you 
wish  the  plant  to  have  in  the  future  and  (2)  the  necessity  of 
reducing  the  leaf  surface  to  correspond  with  the  reduced  roots. 
In  the  case  of  a  shrub  it  is  common  to  cut  back  all  the  branches 
to  a  common  height.  A  tree  is  pruned  so  as  to  favor  retaining 
a  single  central  stem.  Any  tendency  to  fork  should  be  corrected 
by  removing  one  of  the  branches  at  that  point.  Small  branches 
which  will  later  be  overshadowed  and  killed  by  more  vigorous 
ones  should  be  removed  as  well  as  all  lower  branches  which 
will  later  be  objectionable.  Each  of  the  remaining  branches 
should  be  shortened  by  cutting  at  a  point  just  beyond  a  vigorous 
lateral  bud. 

Soak  the  soil  about  the  roots  with  water  occasionally.  Loosen 
up  the  top  soil  if  it  shows  any  tendency  to  become  hard  and 
caked.  . 

Observe  the  growth  of  the  transplants  from  time  to  time  dur- 
ing the  spring.  Report  upon  the  success  or  failure  of  the  attempt 
at  transplanting,  and  try  to  account  for  any  failure  noted. 

[92] 


EXERCISE  75 

WHAT  ARE  THE  SIZE,  SHAPE,  MOTION,  AND  GENERAL 
APPEARANCE  OF  BACTERIA? 

Materials.  Prepare  materials  for  study  of  bacteria  several  days 
before  they  will  be  needed.  Place  a  handful  of  chopped  hay  in  a 
drinking-glass  and  cover  with  water.  Place  several  beans  in  another 
glass  and  add  water  sufficient  to  soak  the  beans  and  half  submerge 
them.  Cover  both  glasses  to  prevent  evaporation  and  stand  in  a 
warm  place.  Microscopes  are  necessary. 

Directions  for  work.  Transfer  to  a  glass  slide  a  small  bit  of 
the  scum  from  the  water  in  which  the  hay  has  been  soaking. 
Examine  with  the  high  power  of  the  microscope. 

The  bacteria  appear  as  very  small  and  almost  transparent 
bodies,  which  may  be  stationary  or  in  motion.  It  is  probable 
that  several  kinds  of  bacteria  will  be  present  in  the  scum.  The 
kind  which  is  commonly  most  abundant  is  rod-shaped  and 
several  times  as  long  as  wide.  Others  may  be  spherical  or  spiral. 

Try  to  find  bacteria  representing  all  three  forms  (see  text- 
book). The  size  of  the  bacteria  cannot  be  measured  without 
special  instruments,  but  they  may  be  compared  with  each  other 
and  with  other  objects  which  pupils  have  previously  viewed  in 
the  microscope ;  or  a  small  object,  as  a  hair,  may  be  introduced 
for  comparison. 

In  studying  the  movements  of  bacteria  it  must  be  remembered 
that  if  all  the  bacteria  in  the  field  of  view  move  together  in 
one  direction,  it  is  due  to  currents  of  water  rather  than  to  any 
proper  bacterial  movement.  Also,  the  bacteria  may  exhibit  an 
interesting  dancing  movement,  called  the  Brownian  motion, 
which  is  exhibited  by  any  small  particles  suspended  in  a  liquid 
quite  independently  of  whether  the  particles  are  living.  Certain 
kinds  of  bacteria  exhibit  a  relatively  rapid  independent  motion 
through  the  water,  commonly  proceeding  in  a  straight  line  until 
coming  in  contact  with  some  other  object. 

Describe  carefully  each  of  the  several  kinds  of  bacteria  found 
as  to  shape,  relative  size,  rate  and  character  of  motion,  and 
whether  the  individuals  occur  in  chains  or  masses,  or  free. 

[93] 


EXERCISE  75  (Continued) 

Examine  some  of  the  larger  ones  carefully  arid  observe  them 
for  some  time  to  discover,  if  possible,  evidences  of  division. 

Repeat  the  study  with  materials  taken  from  the  decaying 
beans.  Also  examine  in  like  manner  any  other  decaying  mate- 
rials found,  but  do  not  write  notes  except  on  the  new  facts 
discovered. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  161-164. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  199,  200. 


[94] 


EXERCISE  76 
TO  STUDY  THE  GROWTH  AND  DISTRIBUTION  OF  BACTERIA 

Materials.  Prepare  a  growth  medium  for  bacteria  by  one  of  the 
following  methods.  The  first  method  is  preferable,  but  the  mate- 
rials may  not  be  available. 

Directions  for  work.  1.  Secure  as  many  petri  dishes  as  will 
be  needed  for  the  solution  of  the  problems  which  are  chosen 
from  the  list  on  pages  96~97.  Sterilize  the  dishes  by  heating  in 
a  steam  sterilizer  for  twenty  minutes  on  each  of  three  days,  or  by 
heating  one  hour  in  a  dry-air  sterilizer  to  a  temperature  suf- 
ficient to  slightly  scorch  cotton  (150°  C.).  The  latter  method 
is  preferable.  Secure  from  the  nearest  bacteriological  laboratory 
as  many  tubes  of  sterile  nutrient  agar  as  you  have  petri  dishes. 
Heat  some  of  the  tubes  in  boiling  water  until  the  agar  is  melted, 
when  the  temperature  may  fall  to  about  45°  C.,  which  will  be 
sufficient  to  keep  the  agar  in  liquid  condition  as  long  as  neces- 
sary. Pour  the  contents  of  each  tube  into  a  petri  dish,  cover, 
and  set  aside  to  cool.  Reserve  the  remainder  of  the  tubes  for 
use  as  directed  below.  Using  gummed  labels,  number  each  dish 
and  tube  used. 

Great  care  must  be  taken  in  the  above  operations  not  to 
allow  bacteria  to  enter  the  agar  either  from  the  air  or  from  any 
other  source.  The  petri  dishes  should  be  covered  before  the 
last  sterilization,  and  the  covers  should  not  be  removed  except 
as  directed  in  performing  the  experiments.  The  agar  may  be 
poured  into  the  dishes  by  lifting  the  cover  on  one  side  and 
inserting  the  end  of  the  test  tube. 

2.  In  case  the  agar  tubes  mentioned  above  cannot  be  secured, 
slices  of  potato  may  be  substituted  in  the  solution  of  certain 
problems.    Boil  a  potato  the  diameter  of  which  is  not  greater 
than  that  of  a  petri  dish,  boiling  for  ten   or  fifteen  minutes 
to  partly  sterilize  the  surface.    Cut  into  thin  •  slices  and .  place 
one  in  each  petri  dish.    Sterilize  in  steam  as  directed   above. 
Sterilization  should  be  repeated  once  or  twice. 

3.  Certain  of  the  problems  suggested  below  may  be  solved 
by  the  use  of  sterilized  milk  as  a  medium  for  the  growth  of 

[95] 


EXERCISE  76  (Continued) 

bacteria.  (For  detailed  directions  see  Caldwell  and  Eikenberry, 
"  Laboratory  Manual  for  Work  in  General  Science,"  Rev.  Ed., 
Exercise  43.) 

A  substitute  for  petri  dishes  may  be  contrived  by  inverting 
a  glass  sauce  dish  over  a  smaller  one,  but  any  substitute  is 
unsatisfactory.  At  least  a  few  petri  dishes  should  be  a  part  of 
the  equipment  of  every  laboratory.  A  steam  sterilizer  may  be 
contrived  by  supporting  the  dishes  above  boiling  water  in  a 
covered  pail,  but  it  is  impossible  to  insure  that  the  material  will 
at  all  times  be  surrounded  by  steam  at  100°  C.  A  small  steam 
sterilizer  is  preferable.  One  or  two  of  the  sterilized  agar  plates 
should  be  retained  as  checks. 

PROBLEMS 

1.  Are  there  bacteria  in  the  air  ?   Expose  one  or  more  of  the 
dishes  to  the  air  by  uncovering  for  a  measured  length  of  time,  as 
twenty  minutes.    Replace  the  cover.    Watch  for  the  appearance  of 
colonies  of  bacteria  in  two  or  three  days.    If  dishes  are  uncovered 
in  different  parts  of  the  building,  a  rough  measure  of  the  abundance 
of  bacteria  may  be  secured. 

2.  Are  bacteria  present  on  one's  person,  as  on  the  hands  ?   Draw 
the  fingers  lightly  across  the  surface  of  the  agar  in  a  dish.    Observe 
later  for  the  development  of  colonies  of  bacteria.    (The  agar  must 
be  well  cooled  else  it  will  stick  to  the  fingers.) 

3.  Repeat  above  after  carefully  washing  the  hands.   What  conclu- 
sions may  be  drawn  regarding  the  sanitary  value  of  washing  ? 

4.  Is  dry  sweeping  a  sanitary  procedure  ?    Expose  a  dish  during 
the  time  the  janitor  is  sweeping  the  laboratory.    If  possible,  expose 
one  just  preceding  sweeping  for  comparison.    Both  should  be  exposed 
for  the  same  length  of  time.    What  are  your  conclusions  ? 

5.  Does  a  vacuum  cleaner  have  sanitary  value  ?  Expose  a  dish  as 
in  Problem  4  in  a  room  in  which  a  vacuum  cleaner  is  being  operated. 

6.  Is  dusting  a  sanitary  procedure?    Expose  one  plate  in  a  room 
that  is  being  dusted  with  a  feather  duster  or  a  dry  cloth.    Expose 
another  similarly  in  a  room  in  which  a  damp  cloth  is  being  used 
to  remove  the  dust. 

[96] 


EXERCISE  76  (Continued) 

7.  What  is  the  effect  of  temperature  upon  bacterial  growth? 
Prepare  six  dishes  in  such  manner  that  they  will  be  approximately 
equally  inoculated  with  bacteria.  This  may  be  done  as  follows  : 
Pour  a  few  drops  of  liquid  from  the  decaying  beans  used  in  the  pre- 
ceding exercise,  or  from  some  similar  source,  into  a  beaker  of  warm 
water.  Stir  the  water  until  it  may  be  supposed  that  the  bacteria 
are  evenly  distributed  through  it.  Melt  the  agar  in  six  tubes,  as 
directed  on  page  95.  When  the  tubes  and  water  by  which  they 
are  surrounded  have  come  to  a  temperature  of  about  45°  C.,  add  to 
each  tube  a  small  measured  quantity  of  the  water  from  the  beaker. 
One  or  two  drops  from  a  medicine  dropper  to  each  tube  will  be  suffi- 
cient. Be  sure  to  add  the  same  number  of  drops  to  each  tube.  Pour 
into  petri  dishes.  Place  two  dishes  in  an  ice  box,  two  others  in 
a  warm  place,  and  let  the  other  two  remain  on  the  laboratory  desk. 
Examine  them  daily  and  note  the  differences  in  size  of  colonies. 
What  is  your  conclusion  ? 

8.  Do  chemical  poisons  prevent  the  growth  of  bacteria  ?   Prepare 
tubes  as  above,  but  in  each  place  small  quantities  of  formalin,  boracic 
acid,  or  other  preservatives.    If  several  tubes  are  prepared  contain- 
ing varying  quantities  of  the  same  preservative,  it  will  be  possible 
to  secure  an  indication  of  the  quantity  of  each  which  is  necessary. 

9.  Are  there  bacteria  in  drinking-water  ?     Proceed  as  in  Prob- 
lem 7,  but  inoculate  tubes  with  drinking-water,  5  to  10  drops,  instead 
of  with  water  from  the  beaker. 

10.  Are  common  drinking-cups  contaminated?  Place  the  edge 
of  a  public  drinking-cup  in  contact  with  the  agar  in  a  dish.  Observe 
results. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  chap.  xi. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  chap.  xiv. 


[97] 


EXERCISE  77 


PHYSIOLOGY  OF  YEAST 

Materials.  Compressed  yeast,  which  must  be  fresh ;  molasses ; 
bottles  ;  flasks  ;  thermometer. 

Directions  for  work.  Mix  one  fourth  of  a  cake  of  compressed 
yeast  with  water,  making  a  thin  paste.  Add  it  to  a  10  per  cent 
solution  of  molasses  in  water.  Add  a  proportionate  amount  of 
yeast  to  pure  water.  Set  both  aside  in  a  warm  place  for  exam- 
ination the  next  day.  It  would  be  well  to  divide  the  molasses 
solution  and  yeast  into  three  parts.  One  of  these  should  be 

reserved  for  use  in  the  next  exer- 
cise and  the  other  two  used  as 
directed  below.  Cover  all  three  of 
them  loosely  in  order  to  prevent 
evaporation. 

When  the  yeast  culture  has 
stood  for  twenty -four  hours  or 
more,  note  the  bubbles  of  gas  rising 
through  the  liquid.  Determine  as 
closely  as  possible  their  place  of 
origin.  In  what  way,  if  any,  do  they  appear  to  be  related  to 
the  yeast?  Collect  some  of  the  gas  as  illustrated.  Test  with 
a  flame  and  with  limewater.  What  gas  is  this  ?  (See  Caldwell 
and  Eikenberry,  "  Elements  of  General  Science,"  Rev.  Ed., 
pp.  71,  72.) 

Put  a  quantity  of  the  solution  into  a  flask  arranged  as 
illustrated.  Heat  until  a  small  amount  of  distillate  has  col- 
lected or  until  the  thermometer  goes  above  80°  C.,  cooling 
and  condensing  the  vapors  in  the  receiving  flask.  Identify  the 
distillate.  Note  its  odor  and  how  rapidly  it  evaporates,  and 
try  to  ignite  some  of  it  soaked  in  filter  paper.  What  is  the 
source  of  the  two  substances  which  have  been  discovered  in 
the  solution  ?  Consider  that  the  three  essential  materials 
in  the  solution  are  water,  sugar,  and  yeast.  Which  of  these 
is  increasing  ?  Which  is  decreasing  ?  Which  is  remaining 
apparently  unchanged? 

[98] 


EXERCISE  77  (Continued) 

Sum  up  in  the  conclusion   of  your   notes  what  you   know 
regarding  the  life-processes  of  yeast. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  232,  233. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  246,  247. 


[99] 


EXERCISE  78 
STRUCTURE  OF  YEAST 

Materials.  Fresh  cake  of  compressed  yeast  and  one  of  the  cul- 
tures from  preceding  exercise  ;  microscopes  ;  slides  and  covers. 

Directions  for  work.  Rub  the  fresh  surface  of  the  yeast  cake 
lightly  across  the  slide.  Add  a  drop  of  water  and  cover  glass. 
Examine  with  a  microscope.  The  small  objects  seen  are  yeast 
plants  and  starch  grains.  If  you  cannot  distinguish  one  from 
the  other,  add  a  bit  of  iodine  solution,  which  will  enable  you 
to  distinguish  the  starch.  (How?)  When  you  are  sure  you 
can  recognize  the  yeast  plants,  prepare  another  slide  without 
iodine.  In  your  notes  tell  what  you  have  learned  about  the 
shape,  relative  size,  color,  and  structure  of  the  yeast  plants. 

Prepare  another  slide  from  the  scum  on  one  of  the  cultures 
of  yeast  in  molasses  solution.  This  yeast  you  know  to  be  in 
'active  condition  (Exercise  77).  Find  •  out,  by  examining  it, 
the  method  by  which  the  number  of  yeast  plants  increases. 
Describe  the  growth  and  reproduction  of  yeast. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  232,  233. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  246,  247. 


[100] 


EXERCISE  79 
PREPARATION  OF  MOLD  CULTURES 

Materials.  Molds  will  grow  on  almost  any  organic  material  if  it 
is  kept  damp.  Their  spores  reach  substances  in  much  the  same 
manner  as  do  bacteria.  In  order  to  have  on  hand  a  variety  of  molds 
for  study,  it  is  advisable  to  prepare  a  number  of  cultures.  These 
should  be  observed  from  day  to  day  and  the  facts  regarding  the 
growth  of  the  molds  recorded.  *  l"  !  i  \  / 


Directions  for  work.  1.  Moisten  a  pisce  pf  .br^d  ^wijjch;  has 
been  exposed  to  the  dust  of  the  air.  Cover  wioL  glass  to  pre- 
vent evaporation  while  allowing  observation. 

2.  Put  a  piece  of  banana  peel  under  a  cover  as  in  1. 

3.  Inclose  a  lemon  or  part  of  one  in  a  similar  manner. 

4.  In  a  dish  place  various  vegetable  scraps  and  cover. 

5.  Cover   a   dish    of   fruit    and   gelatin    dessert,    or    similar 
preparation. 

All  of  the  preparations  suggested  above  should  be  covered 
with  glass  to  allow  observation  without  disturbing  the  mold  or 
exposing  it  to  the  air.  It  is  usually  convenient  to  place  the 
material  in  a  small  shallow  dish  and  cover  with  an  inverted 
drinking-glass.  The  experiments  should  be  placed  in  a  warm 
location. 


[101] 


EXERCISE  80 
BREAD  MOLD 

Materials.  The  rather  coarse  cottonlike  growth  that  commonly 
appears  on  bread  is  referred  to  as  bread  mold  or  black  mold.  It  is 
often  not  the  first  mold  to  appear  on  bread,  but  its  growth  is  so 
vigorous  that  it  soon  covers  up  the  others.  It  may  be  recognized 
by  its  large  white  heads  (sporangia),  which  soon  turn  black.  (See 
textbooks,  undbr  -the  heading  Rhizopus  nigricans,  for  descriptions.) 
It  "may  be'  found  also  in  some  of  the  other  cultures.  If  it  appears 
on"  tie  ,§eflk<ti!)/the  transparency  of  the  medium  will  allow  the  whole 
plant  to  be  seen. 

Directions  for  work.  Study  the  plant  and  its  manner  of 
growth  with  the  naked  eye  and  the  hand  lens.  Describe  it 
carefully.  Look  for  it  in  all  the  other  cultures,  including  the 
cultures  of  bacteria.  If  it  can  be  found  growing  on  the  gelatin 
or  the  agar  cultures  made  in  Exercise  76,  study  the  distribution 
of  the  plant  below  the  surface. 

If  the  plant  has  spread  from  the  bread  to  the  surface  of  the 
containing  dish,  as  commonly  occurs,  note  how  it  advances  into 
new  territory. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  214-217. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  235-239. 


[102] 


EXERCISE  81 
DETECTION  OF  MOLDS  IN  AIR  AND  IN  OTHER  PLACES 

Materials.  Sterilized  petri  dishes ;  one  of  the  common  dessert 
gelatins  which  are  sold  under  various  trade  names,  or  agar  culture 
medium. 

Directions  for  work.  Tests  for  the  presence  of  mold  spores 
in  the  air  and  in  various  media  may  be  made  in  a  manner 
similar  to  that  described  for  bacteria  (Exercise  76).  In  fact,  it 
is  probable  that  many  mold  colonies  were  found  among  the 
bacterial  colonies.  Very  satisfactory  substitutes  for  agar  are 
the  various  sorts  of  gelatin  sold  for  household  use.  If  these 
are  purchased  in  sealed  packages,  they  will  be  practically  sterile 
and  will  need  no  further  sterilization  than  the  boiling  needed 
to  dissolve  them.  Pour  in  shallow  dishes  and  allow  to  cool  in 
the  usual  way,  or  some  of  the  material  may  be  placed  in  sterile 
test  tubes  and  plugged  with  cotton. 

Expose  the  petri  dishes  with  the  culture  medium  in  situa- 
tions similar  to  those  suggested  for  the  bacterial  cultures 
(Exercise  76),  or  inoculate  them  directly  from  other  cultures 
of  mold. 

Keep  several  petri  dishes  or  test  tubes  uninoculated,  as  a 
check  upon  the  sterile  character  of  the  medium.  Set  all  the 
dishes  in  a  warm  place,  where  they  may  be  examined  from 
time  to  time  without  disturbing  them.  From  day  to  day  note 
carefully  the  first  appearance  of  the  colonies  and  the  changes 
that  take  place.  The  cultures  will  afford  the  materials  for  use 
in  the  following  exercises. 


[103] 


EXERCISE  82 
BLUE  MOLD,  OR  BLUE  MILDEW 

Materials.  The  cultures  prepared  in  the  preceding  exercises; 
hand  lens ;  if  possible,  microscope,  slides,  and  covers. 

Directions  for  work.  Study  the  colonies  and  determine  the 
manner  of  increase  in  size  and  the  differences  between  the 
older  and  younger  parts  of  the  colonies.  If  you  have  colonies 
in  a  transparent  medium,  such  as  the  gelatin,  note  the  growth 
of  the  colony  in  the  medium.  If  it  is  possible  to  view  a  colony 
on  gelatin  through  a  low-power  objective  (one-inch  or  two- 
inch)  of  the  microscope,  it  will  be  possible  to  secure  a  very 
good  idea  of  the  whole  plant  in  its  natural  relations. 

What  evidence,  direct  or  indirect,  do  you  have  that  the 
mold  is  drawing  food  from  the  substance  upon  which  it  grows  ? 
Will  it  grow  in  the  dark  ?  Does  it  have  any  observable  effect 
on  the  substance  upon  which  it  grows  ? 

Blue  vitriol  (copper  sulphate,  CuSO4)  is  commonly  used  in 
the  making  of  fungicides.  Place  a  small  piece  of  a  crystal,  not 
much  larger  than  a  pinhead,  near  a  growing  colony  of  blue 
mold  and  note  the  result  after  several  days.  Does  it  have  a 
fungicidal  (fungus-destroying)  action  ?  Do  the  same  with  a 
drop  of  lime-sulphur  mixture  if  you  can  secure  it. 

If  compound  microscopes  are  available,  very  carefully  pick 
up  a  few  fibers  of  the  mold  and  mount  in  a  drop  of  alcohol  on 
a  slide.  Add  water  to  replace  evaporation  of  the  alcohol. 
Examine  the  character  of  the  hyphge,  the  branching,  and  the 
manner  of  forming  spores.  Record  the  principal  facts  in  a 
drawing.  Compare  with  illustrations  in  books  to  discover  the 
name. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  231,  232. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  p.  245. 


[104] 


EXERCISE  83 

YELLOW  MOLD,  OR  YELLOW  MILDEW 
Materials.    Same  as  in  preceding  exercise. 

Directions  for  work.  This  mold  may  be  recognized  by  its 
yellowish  or  olive  color.  It  often  grows  scattered  rather  than 
in  compact  colonies. 

Study  may  be  made  similar  to  that  of  blue  mold.  The 
method  of  formation  of  spores  will  enable  identification  by 
comparison  with  figures  in  books. 


[105] 


EXERCISE  84 
LILAC  MILDEW  — A  PARASITIC  FUNGUS 

Materials.  Leaves  of  lilac  infected  by  the  fungus.  The  fungus 
is  common  on  lilac  leaves  in  the  summer,  giving  them  a  whitish, 
moldy  appearance.  Leaves  should  be  collected  in  June,  when  the 
powdery  appearance  is  first  noted,  and  again  in  autumn,  when  minute 
black  dots  may  be  seen. 

Directions  for  work.  1.  Early  summer  leaves.  Note  the  loca- 
tion of  the  mycelium,  where  it  appears  most  vigorous,  and  its 
relation  to  the  lilac  leaf.  Use  microscope  with  low  power  if 
available,  and  compare  your  observations  with  your  study  of 
the  relation  of  molds  to  the  agar  or  gelatin. 

With  the  hand  lens  note  the  spores,  and,  if  possible,  use 
microscope  to  discover  method  of  formation  of  spores,  as  in 
your  study  of  blue  mold  etc. 

2.  Examine  the  leaves  collected  in  the  autumn  and  deter- 
mine whether  the  black  bodies  are  related  to  the  fungus. 
Mount  for  microscopic  examination  and  crush  by  pressure  on 
the  cover  glass.  What  evidence  do  you  see  of  spores  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  229,  230. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  244,  245. 


[106] 


EXERCISE  85 
WHEAT  RUST— A  DESTRUCTIVE  PARASITE 

Materials.  Stems  and  leaves  of  rusty  wheat  or  oats,  collected 
just  before  harvest ;  wheat  plants  or  stubble  showing  black  rust, 
collected  in  late  summer  or  autumn ;  leaves  of  barberry  showing 
rust. 

Directions  for  work.  1.  Red  rust.  Study  the  distribution, 
shape,  and  general  appearance  of  the  red  spots  on  both  stem 
and  leaves  of  the  wheat  plant.  Write  a  description  intended  to 
assist  in  identifying  the  disease.  Scrape  out  some  of  the  con- 
tents of  one  of  the  red  spots  and  examine  under  high  power  of 
microscope.  Add  to  your  description  the  facts  you  discover. 

If  possible,  examine  rusty  grain  in  the  field  to  determine  the 
character  of  the  injury  by  rust.  Note  especially  the  effect  upon 
the  general  vigor  of  the  plant,  the  strength  of  the  straw,  and 
the  quality  of  the  grain.  If  you  cannot  visit  fields  at  this  time, 
question  farmers  and  others  on  the  above  points. 

Find  out,  by  reading  and  by  talking  to  practical  farmers,  about 
the  effect  of  weather  conditions  upon  rust  and  about  the  sus- 
ceptibility of  different  varieties  of  wheat,  oats,  and  other  grains 
to  rust.  Does  the  information  from  all  sources  appear  to  be 
equally  reliable  ?  Sum  up  what  you  find  to  be  the  facts  on 
this  topic. 

2.  Black  rust.    Study  in  manner  similar  to  that  outlined  for 
the  red  phase.     The  black  rust  is  the  same  plant  as  red  rust, 
but  a  different  kind  of  spore  is  produced  later  in  the  summer. 
As  this  phase  appears  after  harvest,  little  damage  can  be  done 
directly.   Note  dates  of  collection  of  red  and  of  black  rust. 

If  you  can  examine  these  spores  microscopically,  note  their 
characteristics  in  comparison  with  the  red-rust  spores.  Are  they 
in  any  way  particularly  fitted  for  the  season  of  the  year  which 
follows  the  time  of  their  production  ? 

3.  Rust  on  barberry.    The  "  cluster  cups  "  of  wheat  rust  may 
be  found  on  the  under  side  of  barberry  leaves.    Study  and  de- 
scribe  sufficiently  for   identification.     Smaller  growths   of  the 
fungus  may  be  detected  upon  the  upper  side  of  the  leaves. 

[107] 


EXERCISE  85  (Continued) 

These  cluster  cups  are  produced  by  the  same  fungus  that 
produces  red  and  black  rust  in  wheat,  but  the  fungus  grows 
somewhat  differently  in  barberry.  Find  out,  by  reading,  the 
relation  of  barberry  to  rust  in  wheat  fields  and  the  whole  story 
of  the  life  history  of  the  wheat  rust. 

Good  microscopic  sections  will  assist  in  the  study  of  all  three 
of  the  above  forms. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  243-245. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  253-256. 


[108] 


EXERCISE  86 

FUNGI  WHICH  CAUSE  PLANT  DISEASE 
Materials.    Fungi  collected  on  field  trips  ;  books  of  reference. 

Directions  for  work.  Study  and  describe  as  many  kinds  of 
fungi  as  may  be  found  in  field  trips.  Many  of  these  may  be 
identified  with  considerable  certainty  by  inquiry  and  by  refer- 
ence to  books. 

Study  and  describe  each  with  reference  to  the  folio  whig  points: 

1.  General  appearance  on  plant. 

2.  Type  and  extent  of  damage  produced. 

3.  Means  by  which  host  may  be  infected. 

4.  Prevention  of  infection  and  destruction  of  parasite. 

References 

BERGEN  and  CALDWELL     Practical  Botany,  pp.  221,  223,  226-234, 

240-247. 
BERGEN  and  CALDWELL.  Introduction  to  Botany, pp.  239-245,252-256. 

Books  for  Identification 

DUGGAR.    Fungous  Diseases  of  Plants.    Ginn  and  Company. 
STEVENS.    The  Fungi  which  cause  Plant  Disease.   The  Macmillan 
Company. 


[109] 


EXERCISE  87 
A  MUSHROOM 

Materials.  Any  common  mushroom  (or  toadstool)  will  answer. 
If  no  other  material  is  available,  the  common  field  mushroom 
(Agaricus)  may  commonly  be  purchased  in  the  market,  either  fresh 
or  canned,  but,  if  possible,  the  study  should  be  made  on  fresh  mate- 
rial collected  by  the  class. 

Directions  for  work.  Find  mushrooms  in  the  field.  Determine 
whether  they  are  parasites  or  saprophytes  by  field  study.  Note 
the  places  where  they  are  found  and  the  kinds  of  material  to 
which  they  are  commonly  related  and  from  which  they  may 
secure  food.  Find  and  trace  so  far  as  possible  the  fine,  thread- 
like underground  parts.  It  will  be  necessary  to  wash  away 
the  soil  carefully  about  the  base  of  the  mushroom  in  order  to 
discover  the  underground  parts,  or  a  piece  of  the  soil  may 
be  brought  into  the  laboratory  for  examination.  These  under- 
ground hyphse  constitute  the  nutritive  body  of  the  mushroom. 
The  toadstool  is  the  fruiting  body,  producing  the  spores. 

Study  the  fructification,  noting  (1)  the  stalk,  (2)  the  cap, 
(3)  the  gills.  Some  kinds  will  show  also  (4)  a  cup  at  the  base 
of  the  stalk  and  (5)  a  ring  around  the  stalk  below  the  cap. 

Describe  the  mushroom.  If  possible  to  secure  several  kinds, 
describe  each  kind  with  sufficient  clearness  to  enable  one  to 
distinguish  them  from  your  descriptions. 

Identify  any  that  you  find  in  the  field  by  the  use  of  proper 
books. 

References 

BERGEN  and  CALDWELL.    Practical  Botany*  pp.  247-253. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  256-260. 

Book  for  Identification 

PATTERSON    and    CHARLES.     "Mushrooms    and    Other    Common 
Fungi,"  Bulletin  No.  175,  U.  S.  Dept.  Agr.,  1915. 


[110] 


EXERCISE  88 
WOOD-ROTTING  FUNGI 

Materials.  Examine  standing  trees  and  fallen  logs  for  any  large 
fungi  found  growing  upon  living  or  dead  wood.  Bracket  or  shelf 
fungi  and  the  oyster-shell  fungus  are  common.  Collect  these, 
together  with  pieces  of  the  wood  and  bark  to  which  they  are 
attached. 

Directions  for  work.  In  the  laboratory  examine  the  collected 
materials.  Note  that  the  fruiting  bodies  often  have  no  stalk, 
or  a  very  short  one,  and  that  this  stalk  is  in  many  forms 
attached  at  the  edge  of  the  cap  rather  than  in  the  center.  The 
most  marked  feature  of  the  group  to  which  most  of  the  wood- 
rotting  fungi  belong  (Polyporacece)  is  that  the  spores  are  borne 
not  on  gills,  as  in  the  mushrooms  {Agaricacece),  but  in  numerous 
small  pores  found  on  the  under  side.  Any  gill  fungi  found  in 
the  collection  probably  belong  to  the  mushrooms. 

Examine  the  wood  and  bark  for  the  fine,  whitish  fibers  of 
the  mycelium  and  trace  it  through  the  wood  as  far  as  possible. 
Compare  the  fungus-infected  wood  with  sound  wood  as  to  weight, 
hardness,  strength,  and  color. 

Do  you  find  results  of  fungus  attack  in  living  trunks  or 
branches  or  only  in  dead  ones  ?  Is  it  possible  that  these  fungi 
cause  the  death  of  wood  ?  If  so,  what  would  be  their  impor- 
tance with  relation  to  the  lumbering  industry? 

In  the  case  of  any  which  attack  only  dead  wood,  what  is 
their  importance  in  the  forest?  What  is  their  possible  impor- 
tance with  relation  to  telephone  poles,  fence  posts,  and  railway 
ties,  and  in  lumber  yards  ?  What  direct  evidence  have  you  of 
their  actual  importance  in  the  latter  cases  ? 

Reference 

HUMPHREY,  C.  J.    **  Timber-Storage   Conditions,"  Bulletin  No.  510, 
U.  S.  Dept.  Agr. 


[Ill] 


EXERCISE  89 

CLASSIFICATION  OF  FUNGI 
Materials.    Records  of  laboratory  work  on  preceding  exercises. 

Directions  for  work.  Write  a  brief  summary  of  the  distin- 
guishing characters  of  each  of  the  following  subclasses  of  fungi, 
and  add  under  each  subclass  a  list  of  names,  so  far  as  you  know 
them,  of  the  fungi  studied  which  belong  to  that  group. 

CLASS  :  FUNGI 

1.  Subclass  Phycomycetes. 

2.  Subclass  Ascomycetes. 

8.  Subclass  Basidiomycetes. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  chaps,  xiv,  xv. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  chap.  xvi. 


[112] 


EXERCISE  90 
PLEUROCOCCUS  —  THE  GREEN-SLIME  ALGA 

Materials.  Collect  pieces  of  green-stained  bark  from  the  north 
sides  of  trees  or  chips  of  wood  from  fences.  Moisten  some  of  them, 
place  in  a  dish  with  a  glass  cover,  and  expose  to  diffuse  light:  Under 
these  conditions  the  alga  will  grow  indefinitely.  In  most  parts  of 
the  country  the  material  may  be  collected  any  month  of  the  year. 

Directions  for  work.  Examine  a  specimen  of  the  dry  bark 
with  naked  eye  and  hand  lens,  noting  the  powdery  appearance 
of  the  masses  of  Pleurococcus.  Examine  some  of  the  moistened 
material  with  the  microscope,  preferably  after  it  has  had  several 
days  to  grow.  Describe  the  plant. 

Determine  by  microscopic  examination  how  new  plants  are 
produced. 

How  do  you  suppose  Pleurococcus  secures  food  ?  Do  you 
suppose  it  to  be  an  independent  plant,  or  is  it  saprophytic  on 
the  bark  ?  Experiment  in  the  following  way :  Secure  a  piece 
of  porous  earthenware  from  a  broken  flowerpot.  Heat  it  to 
sterilize,  and  place  it  in  a  dish  containing  about  a  quarter  inch 
of  water.  Place  a  small  quantity  of  Pleurococcus  on  the  earth- 
enware and  put  the  whole  in  a.  favorable  place  for  growth. 
Examine  from  time  to  time  for  a  week  'or  two  to  determine 
whether  the  plants  can  grow  without  bark  or  other  similar 
food  material. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,   pp.  188-191. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  221-223. 


[113] 


EXERCISE  91 
A  FUNGUS  PARASITIC  ON  AN  ALGA 

Materials.  Lichens  may  be  readily  found  on  the  bark  of  trees, 
on  fences,  on  stones,  or  on  the  soil.  (See  textbook  illustrations  for 
assistance  in  identification.)  Common  forms  are  greenish  gray,  but 
some  are  almost  black  and  a  few  are  yellow  or  orange. 

Directions  for  work.  Place  a  fragment  of  a  lichen  on  a  glass 
slide  and  tease  it  to  pieces  with  a  needle.  Mount  in  water  and 
examine  with  a  hand  lens,  or,  better,  with  a  microscope.  You 
should  be  able  to  make  out  small  green  cells  and  colorless  fila- 
ments. The  green  cells  are  algae,  which  may  be  one-celled,  like 
Pleurococcus,  or  the  cells  may  be  joined  into  chains  or  filaments. 

How  could  the  alga  secure  food  and  water  ?  How  would 
the  fungus  secure  these  necessities?  Compare  the  condition  of 
lichens  after  a  rain  with  the  condition  of  the  same  plants  during 
a  dry  period.  What  seems  to  be  the  relation  between  the  fungus 
and  the  alga? 

.     Study  and  describe  as  many  kinds  of  lichens  as  you  are  able 
to  find.    The  cups  found  on  some  of  them  are  the  fruiting  bodies. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  235-239. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  247-251. 


[114] 


EXERCISE  92 
SPIROGYRA  —  THE  POND  SCUM 

Materials.  Abundant  in  most  parts  of  the  country  as  a  frothy 
green  scum  on  the  surface  of  shallow  pools.  Fruiting  material,  when 
found,  should  be  preserved  in  formalin. 

Directions  for  work.  With  the  forceps  remove  and  mount  a 
few  of  the  plants.  As  you  are  securing  the  material  note  the 
length  of  the  filament  and  its  appearance  to  the  naked  eye. 

In  studying  the  filament  under  the  microscope  note  the 
arrangement  of  the  cells  and  whether  they  seem  to  be  definitely 
attached  to  each  other.  Also,  is  there  any  differentiation  between 
different  parts  of  the  filament,  or  are  all  parts  alike  ? 

Study  several  cells  in  detail:  observe  (1)  cell,  (2)  peculiar 
spiral  chloroplast  (one  or  more),  (3)  cytoplasm  (lining  the  cell 
wall,  very  transparent,  best  seen  after  staining  with  iodine), 
(4)  nucleus  (imbedded  in  an  irregular  mass  of  cytoplasm  near 
center  of  cell).  This  mass  of  cytoplasm  is  suspended  by  delicate 
threads  running  from  it  to  the  cytoplasm  next  the  cell  wall. 
The  space  not  occupied  by  the  cytoplasm  is  filled  with  cell  sap 
(mainly  water)  and  is  called  the  cell  vacuole. 

Do  you  find  any  cells  which,  from  their  length  or  for  any 
other  reason,  appear  to  have  been  lately  formed  by  division? 
If  so,  draw  them  in  outline. 

Draw  one  or  two  cells  in  detail. 

How  would  this  plant  secure  the  essential  materials  for  its 
nutrition  ?  Is  there  any  evidence,  such  as  giving  off  oxygen  or 
presence  of  starch  in  the  cells  associated  with  the  chloroplasts, 
that  it  carries  on  photosynthesis  ?  Devise  your  own  methods 
for  determining  these  facts. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  191-193. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  223-225. 


[115] 


EXERCISE  93 
REPRODUCTION  IN  SPIROGYRA 

Materials.  Spirogyra  reproduces  freely  in  the  spring  or  early 
summer.  Material  should  be  collected  at  that  time,  examined,  and, 
if  showing  reproductive  stages,  should  be  preserved  for  use  in  the 
laboratory  when  fresh  material  is  not  available. 

Directions  for  work.  It  is  not  usual  to  be  able  to  find  Spirogyra 
in  reproductive  condition  just  when  wanted.  For  that  reason 
you  will  be  supplied  with  preserved  material  in  bottles.  Do  not 
remove  more  material  than  needed. 

When  you  have  mounted  a  slide  in  the  usual  way,  examine 
it  under  the  low  power  for  reproductive  stages  (see  textbook). 
If  you  are  quite  confident  that  there  is  nothing  of  interest  on 
the  slide,  wipe  the  material  off  and  prepare  another  promptly. 

Find  and  draw  the  following  stages  in  the  formation  of  the 
spore  : 

1.  Protuberances  from  cells  of  two  adjacent  plants  not  yet 
united. 

2.  Protuberances  united. 

3.  Gamete  passing  through  the  tube. 

4.  Completed  spore. 

Draw  stages  in  whatever  order  you  find  them,  but  label 
properly  and  try  to  arrange  in  order. 

This  method  of  spore  formation  by  the  union  of  two  cells  is 
called  sexual  spore  formation,  or  sexual  reproduction. 

In  this  case  is  there  any  visible  difference  between  the  two 
filaments,  or  the  conjugating  cells,  corresponding  to  the  male 
and  female  sexes  in  higher  "plants  or  animals  ?  When  the  spores 
have  been  formed  do  you  note  any  difference  between  the 
filaments?  Since  each  spore  is  a  single  cell,  formed  by  the 
union  of  two  cells,  how  has  the  total  number  of  cells  changed? 
Would  the  spores  possess  any  advantage  over  the  filaments  if 
the  pond  should  dry  up  ? 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  193,  194. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  224,  225. 

[116] 


EXERCISE  94 
EDOGONIUM 

Materials.  This  alga  may  be  found  attached  to  sticks  and  stones 
in  ponds  and  streams.  Fruiting  material  should  be  preserved 
when  found. 

Directions  for  work.  Compare  the  cells  with  those  of  Spirogyra. 
Examine  the  attached  end  of  the  filament  for  the  peculiar  hold- 
fast. This  is  particularly  well  seen  on  young  filaments. 

If  the  material  is  fruiting,  some  of  the  filaments  will  contain 
thick-walled  sexual  spores  similar  to  those  seen  in  Spirogyra. 
Do  all  cells  of  the  filament  form  sexual  spores  ?  Other  fila- 
ments may  show  these  in  earlier  stages,  before  the  thick  wall 
has  formed,  illustrating  all  the  stages  in  the  transformation  of 
an  ordinary  vegetative  cell  into  a  sex  cell  (egg). 

Certain  cells  of  the  same  filament  or  of  other  filaments 
may  be  found  wjiich  have  divided  transversely,  forming  several 
smaller  cells.  In  each  of  these  are  formed  two  small  sex  cells 
(sperms).  These  escape  into  the  water  and  may  swim  to  the 
large  sex  cells  and  unite  with  them,  one  small  cell  uniting  with 
one  large  one.  Afterward  the  thick  wall  forms. 

Can  you  distinguish  the  sexes  here  ?  Is  there  any  consider- 
able amount  of  food  material  stored  in  either  sperm  or  egg  or 
in  the  spore  ?  What  is  the  advantage  ? 

Reference 

BERGEN  and  CALDWELL.   Practical  Botany,  p.  202. 


[iir 


EXERCISE  95 
STUDY  OF  GREEN  ALG.E 

Materials.  Collections  brought  in  from  field  trips  along  streams, 
ponds,  and  lakes. 

Directions  for  work.  Familiarize  yourself  with  the  great  variety 
of  forms  among  the  algae  by  examining  with  the  microscope  all 
the  materials  collected,  including  the  sediments.  A  large  num- 
ber of  kinds  of  algae  will  be  found.  Some  of  these  may  be 
recognized  by  reference  to  the  textbook.  Those  who  are  more 
interested  may  be  able  to  identify  others  by  the  use  of  the 
proper  books. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  188-206,  212. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  chap.  xv. 

Book  for  Identification 

COLLINS.   Green  Algse  of  the  United  States.   Tufts  College  Studies. 


[118] 


EXERCISE  96 
VEGETATIVE  STRUCTURE  OF  A  MOSS  PLANT 

Materials.  Growing  moss  plants  collected  by  the  class  on  field 
trips ;  preserved  materials  to  supplement  the  collections  if  necessary. 

Directions  for  work.  Study  the  plants  with  the  object  of 
finding  out  how  well  fitted  they  are  to  perform  their  nutritive 
work  in  competition  with  other  plants  and  in  the  struggle  against 
unfavorable  natural  conditions.  Compare  constantly  with  what 
you  know  of  simpler  plants  (algse)  and  more  complex  plants 
(flowering  plants). 

1.  How  does  the  moss  plant  secure  food?    Does  it  have 
chlorophyll  ?   stem  ?   leaves  ?   In  what  way,  if  any,  is  it  better 
equipped  than  the  common  algse  to  expose  a  large  surface  to 
the  light  without  being  readily  shaded  ?    In  a  competition  for 
light  between  an  alga  like  Spirogyra  and  a  moss  growing  in  the 
water,  as  peat  moss,  which  would  probably  survive  ?    Which, 
in  the  case  of  a  land  alga,  like  Pleurococcus  or  Vaucheria,  and 
a  common  moss  ? 

Would  a  moss  or  a  flowering  plant  have  the  better  oppor- 
tunity to  secure  light  and  carry  on  photosynthesis?  Can  you 
find  in  the  moss  plant  strengthening  tissue  such  as  you  found 
in  flowering  plants,  which  would  support  large  leaves  and  tall 
stems?  What  is  your  opinion  of  the  place  of  the  mosses  in 
the  competition  for  light  among  plants  ? 

2.  Consider  the  problems  of  securing  and  retaining  water 
in  relation  to  the  moss  plant,  keeping  in  mind  particularly  the 
mosses  that  live  upon  land. 

What  equipment  does  the  moss  plant  have  for  securing  water 
from  the  soil?  Might  it  be  able  to  secure  water  from  even  a 
very  small  distance  beneath  the  surface  ?  How  does  its  equip- 
ment for  absorption  from  the  soil  compare  with  that  of  the 
algse  ?  with  that  of  the  flowering  plants  ? 

How  well  is  the  moss  adapted  to  retain  water  ?  Does  it  have 
an  epidermis,  layers  of  hairs,  cuticle,  or  other  protective  devices 
such  as  you  found  on  leaves  and  other  parts  of  flowering  plants? 
Would  you  expect  to  find  a  high  or  a  low  rate  of  transpiration 

[119] 


EXERCISE  96  (Continued) 

from  mosses  in  dry  air  ?  Does  the  moss  have  a  well-developed 
transportation  system  for  water,  similar  to  the  fibrovascular 
bundles  of  higher  plants,  which  would  be  capable  of  trans- 
porting water  for  a  large  leaf  area?  Upon  the  basis  of  these 
facts,  can  you  account  for  the  restriction  of  the  mosses,  com- 
monly, to  locations  with  moist  soil  and  moist  air.  Do  you 
consider  them  to  be  more,  or  less,  well  fitted  to  grow  upon  land 
than  the  algse  ?  than  the  flowering  plants  ? 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  257-260. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  262-264. 


[120] 


EXERCISE  97 
REPRODUCTION  OF  MOSSES 

Materials.  Collections  of  moss  bearing  the  long-stalked  spore 
cases,  and  material  with  archegonia  and  antheridia;  prepared  sec- 
tions of  archegonia,  antheridia,  and  sporophytes. 

Directions  for  work.  Most  of  the  facts  of  the  reproduction  of 
mosses  can  be  worked  out  only  by  the  aid  of  the  compound 
microscope.  With  the  exception  of  1  this  exercise  had  better 
be  omitted  unless  the  class  is  an  advanced  one. 

1.  Some  of  the  moss  plants  will  bear  at  the  top  a  leafless 
stem  from  one  to  three  inches  tall,  with  an  enlargement  at  the 
top.    When  disturbed,  clouds  of  spores  may  be  given  off  from 
the  enlargement,  or  sporangium.   These  are  sexual  spores. 

2.  Antheridia  and  archegonia.    These  may  be  dissected  out 
from  the  tips  of  the  leafy  stems  with  needles  and  examined 
by  the  aid  of  the  microscope.    A  more  careful  study  can  be 
made  from  stained  sections.    (See  textbook  for  details.) 

3.  The   sporangium   and   stalk   (sporophyte)   grows  from  a 
fertilized  egg.    (See  textbook.)    Development  of  the  sporophyte 
may  be  followed  in  sections. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  260-265. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  264-266. 


[121] 


EXERCISE  98 
VEGETATIVE  ORGANS  OF  THE  FERN 

Materials.  Entire  fern  plants,  either  wild  or  potted  (young  plants 
about  six  inches  high  will  answer  admirably);  sections  of  under- 
ground stem  of  fern ;  sections  of  fern  leaves. 

Directions  for  work.  Study  the  fern,  as  you  did  the  moss, 
with  reference  to  its  equipment  for  its  vegetative  work. 

1.  How  does  the  fern's  equipment  for  photosynthesis  compare 
with  that  of  moss  and  alga?   with  that  of  flowering  plants? 
Consider  ability  to  rise  above  competitors,  supporting  tissue, 
amount  of  surface  exposed,  palisade  tissue,  intercellular  spaces 
in  leaf,  and  stomata  allowing  entrance  of  carbon  dioxide. 

2.  How  does  the  fern's  equipment  for  securing,  transporting, 
and  retaining  water  compare  with  that  of  the  other  kinds  of 
plants  ?    Consider  roots  and  root  hairs,  fibrovascular  bundles, 
epidermis,  hairs,  cuticle,  and  veins. 

3.  From  what  you  have  seen  and  read  regarding  the  places 
where  ferns  grow,  their  numbers,  size,  and  distribution,  what 
is  your  opinion  of  their  ability  to  compete  with  other  plants 
in  the  struggle  for  existence? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  274-280. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  269-273. 


[122] 


EXERCISE  99 
REPRODUCTION  AND  DISPERSAL  OF  THE  FERN 

Materials.  Fern  leaves  with  fruit  dots  on  under  side  may  be 
secured  either  in  the  woods  or  in  greenhouses. 

Directions  for  work.  Study  the  arrangements  of  the  fruit  dots 
on  the  different  leaves  available.  This  is  one  of  the  characters 
that  assist  in  distinguishing  different  species.  Record  in  notes 
or  sketches  the  different  plans  of  distribution  found.  Record 
also  the  shape  and  attachment  of  the  scale  which  covers  the 
fruit  dots. 

Scrape  off  onto  a  glass  slide  the  contents  of  one  of  the  dots, 
selecting  one  that  has  not  yet  turned  brown.  Examine  with  a 
hand  lens  and  microscope.  The  sporangia  will  be  seen,  and 
possibly  the  spores  may  be  seen  within  them.  If  a  compound 
microscope  is  used,  crush  some  of  the  sporangia  by  pressure  on 
the  cover  glass  and  observe  the  spores.  These  are  asexual  spores. 

Study  dispersal  by  the  following  method:  Place  a  fern  leaf 
with  almost  ripe  sporangia  on  a  piece  of  white  paper,  fruiting 
surface  downward.  Allow  it  to  remain  undisturbed  for  a  day  or 
two.  The  drying  of  the  sporangia  will  cause  them  to  open  and 
shed  their  spores.  Examine  the  paper  for  spores  and  for  evi- 
dence that  they  are  forcibly  discharged  by  the  sporangia.  What 
would  be  the  result  as  to  dispersal  of  the  spores  if  they  were 
similarly  discharged  from  a  leaf  in  position  on  the  plant  ?  What 
if  the  wind  were  blowing? 

Some  of  the  spores  may  be  scraped  from  the  paper  and  placed 
on  a  slide  for  examination  with  the  microscope. 

Common  ferns  may  be  readily  identified  by  reference  to 
proper  books. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  280-282. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  273,  274. 

Book  for  Identification 

GRAY.     New   Manual   of   Botany,  7th   edition.     American   Book 
Company. 

[123] 


EXERCISE  100 
THE  FERN  GAMETOPHYTE 

Materials.  Fern  gametophytes  may  be  found  in  greenhouses 
where  ferns  have  been  shedding  spores.  They  are  small,  delicate, 
heart-shaped  green  bodies  not  more  than  an  eighth  or  a  quarter  of 
an  inch  in  diameter.  (See  textbooks  for  illustrations.)  Fern  gameto- 
phytes are  rarely  found  in  the  field  even  by  experienced  collectors. 
The  exercise  may  well  be  given  as  a  demonstration  with  any  but 
the  most  advanced  classes. 

Directions  for  work.  The  fern  spores  do  not  grow  into  plants 
like  the  original.  A  spore  when  germinated  produces  a  small 
heart-shaped  plant  called  the  fern  gametophyte  (or  the  prothal- 
lus).  Examine  a  gametophyte,  noting  its  characteristics. 

Consider  its  ability  to  secure  food  and  water  and  its  general 
ability  to  succeed  in  the  struggle  for  existence,  using  the  same 
outline  as  was  used  in  the  study  of  the  moss  plant.  How  does 
the  gametophyte  generation  of  the  fern  compare  with  the  gen- 
eration of  the  fern  just  studied  (sporophyte)  in  equipment  for 
successful  competition  with  other  plants  ? 

The  gametophyte  produces  sexual  cells  (gametes)  which 
unite  to  form  sexual  spores.  From  these  the  familiar  spore- 
bearing  plant  (Exercise  99)  is  produced.  Young  sporophytes 
may  be  found  attached  to  some  of  the  gametophytes. 

In  the  life  history  of  the  fern,  therefore,  sporophyte  and 
gametophyte  alternate.  Is  the  gametophyte  a  weak  or  a 
strong  link  in  the  life  history? 

The  leafy  moss  plant,  with  which  you  have  been  comparing 
the  fern,  is  a  gametophyte;  the  spore  case  and  stalk  are  the 
sporophyte  generation.  The  moss  sporophyte  is  parasitic.  Com- 
paring the  fern  with  the  moss,  has  the  sporophyte  become  more, 
or  less,  important  ?  Has  the  gametophyte  become  more,  or  less, 
important  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  282-286. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  p.  274. 

[124] 


EXERCISE  101 
VEGETATIVE  STRUCTURE  OF  THE  PINE 

Materials.  Branches  with  leaves  and  cones ;  sections  of  wood 
and  leaves,  either  free-hand  or  microtome  cut. 

Directions  for  work.  Determine  whether  the  pine  tree  is 
structurally  well  equipped  with  the  tissues  needful  to  perform 
its  nutritive  work  in  competition  with  the  flowering  plants. 
Proceed  as  in  the  study  of  mosses  and  ferns. 

Examine  standing  trees  with  regard  to  the  extent  of  root 
system,  the  height  and  strength  of  stems,  and  the  amount  of 
leaf  surface. 

Examine  the  leaves  and  stems  in  more  detail,  comparing  with 
your  descriptions  and  drawings  of  leaves  and  stems  of  flowering 
plants  and  ferns. 

1.  Leaves.    Note  arrangement  in  clusters  and  number  in  each 
cluster.    Note  size   and  shape   of  leaves.    Ascertain   the  facts 
regarding  epidermis  and  cuticle,  palisade  tissue,  stomata  and 
internal  air  passages,  and  veins.    Do  the  leaves  seem  suited  to  a 
dry  climate  or  a  moist  one  ?    Is  the  cold  northern  winter  a  dry 
or  a  moist  season  so  far  as  the  leaves  are  concerned? 

2.  Stem.    Compare  the  gross  and  microscopic  structure  of  the 
wood  with  that  of  dicotyledonous  stems  (Exercise  7),  using 
your  notes  and  drawings.    What  are  the  points  of  resemblance 
between  gymnosperm  and  dicotyledonous  stems  ?   What  are  the 
points  of  difference  ? 

3.  How  well  equipped  does  the  pine  tree  appear  to  be  in  com- 
parison with  the  flowering  plants  studied  earlier  in  the  course  ? 

Look  up  the  facts  of  the  actual  success  of  the  pines  and  see 
whether  the  facts  agree  with  your  conclusion  given  above. 
Refer  to  textbooks,  encyclopedias,  geographies,  etc.  Note  such 
facts  as  the  geographic  distribution  of  the  pines,  the  area  of 
the  pine  forests,  the  abundance  of  individuals  in  the  forest, 
and  the  size  and  age  of  individual  trees. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  299-306. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  268-289. 

[125] 


EXERCISE  102 
REPRODUCTION  OF  THE  PINE 

Materials.  Cones  of  the  season  containing  seeds,  one-year-old 
cones  on  branches,  and  branches  with  young  staminate  and  pistillate 
cones ;  pinon  seeds. 

Directions  for  work.  The  familiar  pine  tree  is  the  sporophyte 
generation,  bearing  two  kinds  of  asexual  spores,  one  of  which 
is  illustrated  by  the  pollen  grains.  The  gametophyte  generation 
is  so  reduced  that  it  can  be  studied  only  by  the  aid  of  the 
compound  microscope.  The  gametophytes  will  not  be  included 
in  the  laboratory  work. 

1.  Staminate  cones.    The  cones  are  composed  of  a  central  axis 
bearing  overlapping  leaves.    Split  a  cone  through  the  center  to 
see  the  attachment  of  the  scales  to  the  axis.    Pick  off  one  of 
these  scales,  or  stamens,  and  find  the  two  pollen  sacs  (sporangia) 
on  the  under  surface.  Make  a  diagram  to  show  the  arrangement 
of  the  scales  on  the  stem  and  another  to  show  the  form  of  the 
stamen  and  its  pollen  sacs. 

Break  open  one  of  the  pollen  sacs  and  mount  the  pollen  for 
observation  with  the  microscope.  Note  the  two  wings  which 
assist  in  distribution  by  the  air. 

The  pine  is  wind-pollinated.  Is  this  an  economical  method 
so  far  as  amount  of  pollen  required  is  concerned  ?  Place  a 
cluster  of  fresh  cones  which  have  riot  shed  their  pollen  in  a  cup 
and  allow  them  to  remain  for  several  days.  Note  the  quantity 
of  pollen  collected. 

2.  Young  pistillate  cones.    Note  the  arrangement  of  the  scales. 
Remove  several  and  find  the  two  ovules  on  the  base  of  each. 
Make  a  diagram  showing  the  arrangement  of  the  scales  on  the 
axis  and  the  position  of  the  ovules  on  the  scales. 

Are  these  ovules  inclosed  in  an  ovary  as  are  those  of  flowering 
plants?  Can  the  pollen  grains  which  the  wind  deposits  on  these 
cones  come  into  actual  contact  with  the  ovules,  or  is  there  a 
style,  stigma,  etc.,  as  in  flowering  plants? 

3.  One-year-old  cones.    Examine  scales  from  these  to  see  the 
growth  in  scale  and  ovules,  now  become  seeds. 

[126] 


EXERCISE  102  (Continued) 

4.  Two-year-old  cones.    Examine  the  scales  and  seeds.    Draw 
a  scale   with   seeds   in  position,  showing   wings  of  the   seeds. 
Experiment  with  the  seeds,  as  you  did  with  the  fruits  of  maple 
etc.,  to  determine  their  adaptation  for  dispersal  by  wind.    If 
mature  cones  which  have  not  shed  their  seeds  can  be  secured, 
allow  several  of  them  to  lie  on  the  table  for  several  days  and 
note  how  the  seeds  are  released  from  the  cones. 

5.  The  embryo.    Carefully  pick  off  the  hard  outer  coating  of 
a  seed  and  remove  the  white  interior.    Bit  by  bit,  pick  off  the 
outer  part  of  the  white  interior  until  you  come  to  the  embryo 
within.    If  you  fail  on  the  first  one,  try  another.    The  large 
seeds  of  the  pin  on,  often  sold  under  the  name  of  fine  nuts,  are 
particularly  satisfactory  for  this  study.    Make  a  drawing  of  the 
embryo,  showing  stem  and  leaves.    Make   a  diagram  showing 
relative  position  of  embryo,  food  supply,  and  seed  coat. 

Does  the  seed  of  the  pine  appear  to  be  equivalent  to  the 
seeds  of  flowering  plants  which  you  have  studied,  on  such 
points  as  means  of  dispersal,  protective  covering,  food  supply, 
and  condition  of  embryo  ?  Do  you  find  any  weak  point  in  the 
life  history  of  the  pine  similar  to  the  gametophyte  generation 
of  the  fern? 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  306-311. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  289-292- 


[127] 


EXERCISE  103 
THE  GYMNOSPERM  GROUP 

Materials.  Collect  branches,  with  fruit  if  possible,  of  any  needle- 
leaved  evergreen  trees  in  your  vicinity. 

Directions  for  work.  Describe  each  of  the  kinds  found,  being 
careful  to  state  clearly  the  characteristics  which  distinguish  each. 

Describe  the  group  as  a  whole,  emphasizing  the  character- 
istics which  are  common  to  all  the  gymnosperms  you  know. 

The  gymnosperms  which  are  native  to  the  United  States  may 
be  readily  identified  by  the  use  of  the  books  listed  under  Books 
for  Identification  below. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  chap,  xviii. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  pp.  282-296. 

Books  for  Identification 

BRITTON  and  BROWN.  Illustrated  Flora  of  the  Northern  States  and 

Canada.    Charles  Scribner's  Sons. 
CHAPMAN.    Flora  of  the  Southern  United  States.    American  Book 

Company. 
COULTER    and    NELSON.     Manual    of    Rocky    Mountain    Botany. 

American  Book  Company. 
GRAY.    New   Manual   of   Botany,    7th   edition.     American   Book 

Company. 
HOUGH.   Handbook  of  the  Trees  of  the  Northern  States  and  Canada. 

Published  by  the  author. 
PIPER  and  BEATTY.    Flora  of  the  Northwest  Coast.     State  College 

of  Washington. 

RYDBERG.  Flora  of  Colorado.    Bulletin  No.  100,  Colo.  Agr.  Exp.  Sta. 
SUDWORTH.    "  Trees  of  the  Pacific  Slope."     Forest  Service,  U.  S. 

Dept.  Agr. 


[128] 


EXERCISE  104 
THE  STAMEN  OF  A  FLOWERING  PLANT  (ANGIOSPERM) 

Materials.  Stamens  from  flower  of  lily  or  similar  plant,  but 
stamens  from  almost  any  flower  can  be  used;  slides  showing  cross 
sections  of  anthers  with  pollen. 

Directions  for  work.  The  structure  of  the  vegetative  parts  of 
the  flowering  plants  (properly  called  angiosperms)  has  been 
studied  previously  (Exercises  1-74),  as  is  also  true  of  some 
of  the  facts  about  the  flowers.  Only  a  few  of  the  details  of 
reproduction  will  be  presented  here.  The  gametophytes  of 
angiosperms  are  more  reduced  than  those  of  gymnosperms. 

Examine  a  stamen  which  has  not  shed  its  pollen  and  note 
the  pollen  sacs  (sporangia).  How  many  are  there?  If  the 
anther  is  cut  across  with  a  sharp  knife,  the  relation  of  parts 
may  be  the  more  readily  seen ;  use  a  lens. 

If  you  have  slides  with  cross  sections  of  anthers,  examine 
them  with  the  low  power  of  the  microscope.  Make  a  diagram 
showing  the  shape  and  relation  of  parts. 

Place  some  of  the  pollen  grains  on  a  slide  without  water 
or  a  cover  glass.  Examine  with  the  low  power  of  the  micro- 
scope. If  you  will  set  the  microscope  in  a  brightly  lighted 
place  and  turn  the  mirror  so  that  no  light  is  reflected  from 
below,  the  pollen  grains  will  be  seen  in  their  natural  colors 
against  a  dark  background. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  110,  111. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  129,  299. 


[129] 


EXERCISE  105 
POLLINATION 
Materials.    Flower  of  lily,  or  other  large  flower. 

Directions  for  work.  Touch  with  a  camel' s-hair  brush  an 
anther  which  is  shedding  pollen,  and  then  bring  the  brush  into 
contact  with  a  stigma  on  which  no  pollen  is  visible.  Examine 
the  stigma  after  touching  with  the  brush.  Do  you  find  any 
evidence  that  pollen  can  be  transferred  by  this  means?  How 
may  the  lily  be  pollinated  in  nature  ? 

Examine  stigmas  in  flowers  of  different  ages,  noting  whether 
there  is  anything  in  the  condition  of  the  stigma  at  any  time 
that  favors  the  adherence  of  the  pollen.  If  such  a  condition  is 
found,  does  it  occur  at  the  time  the  anthers  in  the  same  flower 
are  shedding  pollen,  before  shedding,  or  after?  How  would 
this  affect  the  possibility  of  self-pollination  ? 

Make  a  similar  examination  of  flowers  of  several  different 
kinds  with  reference  to  the  relation  between  the  time  of  shedding 
pollen  and  the  condition  of  the  stigma. 

References 

BERGEN  and  CALDWELL.  Practical  Botany,  pp.  325,  326,  chap.  viii. 
BERGEN  and  CALDWELL.  Introduction  to  Botany,  pp.  300, 301,  chap.  x. 


[130] 


EXERCISE  106 

GERMINATION  OF  POLLEN  GRAIN 
Materials.    Sweet-pea  flowers  ;  cane-sugar  sirup. 

Directions  for  work.  Mount  pollen  on  a  slide  in  cane-sugar 
sirup  and  cover  with  a  cover  glass.  To  avoid  crushing  the 
pollen  grains  place  small  pieces  of  broken  cover  glass  under 
the  edges  of  the  cover.  Set  aside  in  a  covered  dish  containing 
a  sponge  saturated  with  water  in  order  to  prevent  evaporation. 
Examine  from  time  to  time. 

The  sugar  sirup  should  be  made  by  dissolving  cane  sugar  in 
water.  Sweet-pea  pollen  will  commonly  grow  in  sirup  with  a 
concentration  of  from  10  to  15  per  cent.  It  is  advisable  to  pre- 
pare a  series  of  slides  with  sirups  of  differing  strengths  in  order 
to  be  sure  that  some  of  them  will  show  germination. 

References 

BRRGEN  and  CALDWELL.  Practical  Botany,  pp.  115-117,  325-326. 
BERGEN  and  CALDWELL.  Introduction  to  Botany,  pp.  134-136, 300-302- 


[131] 


EXERCISE  107 

OUTLINE  FOR  THE  STUDY  OF  COMMON  FLOWERING 

PLANTS 

Materials.  The  plants  should  be  collected  in  the  field  by  the 
pupils  if  that  is  possible.  One  object  of  the  work  should  be  to 
secure  an  acquaintance  with  the  plants  of  the  neighborhood.  The 
amount  of  this  work  must  be  adjusted  by  the  teacher  to  the  time 
available.  Do  not  use  for  these  studies  rare  plants  or  those  in 
danger  of  extermination. 

Directions  for  work.  Study  each  plant  systematically  and 
describe  it  carefully,  noting  particularly  the  distinguishing 
characteristics. 

1.  General  appearance  in  the  field:  herb,  vine,  shrub,  tree. 

2.  Stem :  woody  or  herbaceous ;  character  of  internal  struc- 
ture; height;  character  of  branching;  peculiarities  of  buds,  bark, 
etc.,  that  might  assist  in  identification. 

3.  Root  system,  so  far  as  you  are  able  to  learn  about  it. 

4.  Leaves:  arrangement,  size,  form,  venation. 

5.  Flowers:  arrangement,  color,  form. 

6.  Calyx  and  corolla. 

7.  Stamens. 

8.  Pistil  and  fruit. 

9.  Pollination:    manner    of   pollination    and   characteristics 
that  might  assist  in  securing  cross-pollination ;  observed  visits 
of  insects  etc. ;  means  of  preventing  self-pollination. 

10.  Seeds  and  seed  dispersal;  record  of  field  observations 
on  dispersal. 

11.  Name :  to  be  secured  by  the  aid  of  manuals  and  floras. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  chap,  xx,  review  chaps. 

iii-ix. 

BERGEN  and  CALDWELL.   Introduction  to  Botany,  chap,  xviii,  review 
chaps,  ii-xiii. 


[132] 


EXERCISE  108 
ROOT  TUBERCLES 

Materials.  Roots  of  clover,  alfalfa,  or  other  legumes.  The  roots 
should  be  dug  carefully  in  order  that  the  tubercles  may  not  be 
broken  off  in  freeing  the  roots  from  the  soil. 

Directions  for  work.  The  tubercles  are  small  rounded  or 
oval  bodies  in  connection  with  the  smaller  roots.  They  are 
easily  seen. 

After  noting  their  abundance,  form,  size,  and  color,  break  one 
of  them  open  and  examine  them  microscopically  for  bacteria. 

Examine  roots  of  a  number  of  members  of  the  pea  family 
(Legttminosce)  that  may  be  found,  to  discover  how  common  is 
the  possession  of  tubercles. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  374-378. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  204-206. 


[133] 


EXERCISE  109 
VARIATION  IN  CULTIVATED  PLANTS 

Materials.  An  exercise  similar  to  the  following  may  be  worked 
out  with  almost  any  cultivated  or  wild  plant.  Ears  of  corn  are  sug- 
gested as  being  readily  available  at  any  season  of  the  year  in  most 
parts  of  the  country.  Secure  ears  of  corn  from  the  crib  without 
selection  in  order  that  the  sample  may  represent  the  actual  char- 
acter of  the  crop  as  nearly  as  possible.  At  least  a  hundred  ears 
should  be  included  in  the  study  by  the  class  if  the  number  of  pupils 
is  great  enough  to  make  the  study  without  using  excessive  time. 
Popcorn  or  sweet  corn  may  be  used  as  well  as  field  corn. 

If  it  is  not  desired  to  use  corn,  other  problems  may  be  taken  up 
based  upon  other  plants.  The  following  are  suggested :  weight  of 
grains  in  heads  of  wheat,  oats,  etc. ;  number  of  heads  per  plant ; 
number  of  grains  per  head;  height  of  cornstalks;  height  of  corn 
ears  from  ground ;  height  of  timothy  plants ;  number  of  timothy 
stems  in  a  clump ;  length  of  timothy  heads  on  different  plants ; 
number  of  cotton  bolls  per  plant ;  weight  of  cotton  per  plant ;  length 
of  cotton  fiber. 

Directions  for  work.  Weigh  each  ear  of  corn.  Shell  the  grains 
off  the  cob  and  weigh  grains  and  ear  separately.  Tabulate  as 
follows  and  correct  any  error  that  appears: 

Weight  of  entire  ear 

Weight  of  grains  only 

Weight  of  cob  only 

Sum  of  grains  and  cob 

Error 

Tabulate  the  weights  of  grains  of  all  the  ears  weighed  by 
members  of  the  class  in  the  following  blank : 

Number  of  ears  with  grains  weighing 

Ig.to49g 

50  g.  to  99  g 

100  g.  to  149  g 

150  g.  to  199  g 

200  g.  to  249  g 

250  g.  to  299  g 

[134] 


EXERCISE  109  (Continued) 

From  the  table  of  distribution  above,  answer  the  following 
questions :  How  wide  is  the  variation  in  this  group  of  ears  ? 
Are  the  variations  great  enough  to  be  of  practical  importance? 
How  largely  would  the  yield  be  affected  if  all  the  ears  were 
like  the  smallest?  if  all  were  like  the  largest?  In  what  groups 
do  most  of  the  ears  fall  ?  Which  ears  would  probably  be  selected 
for  use  in  an  effort  to  improve  the  breed  of  corn  ? 

On  cross-section  paper  make  a  graph  representing  the  facts 
shown  on  the  table  above. 

References 

BERGEN  and  CALDWELL.  Practical  Botany,  pp.  413,  414,  417,  418. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  173, 174, 181-184. 
CALDWELL  and  EIKENBERRY.    Elements  of  General  Science,  pp.  290- 

302.    Ginn  and  Company. 
DAVENPORT.   Domesticated  Animals  and  Plants,  chap.  viii.  Ginn  and 

Company. 


[135] 


EXERCISE  110 
PLANT  BREEDING 

Materials.  Ears  of  corn  from  the  preceding  exercise.  The  exer- 
cise will  require  a  plot  of  ground,  either  at  the  home  of  a  pupil  or 
in  the  school  garden.  The  results  of  each  experiment  will  be  avail- 
able to  the  class  of  the  following  year  and  may  be  made  the  basis  of 
the  study  in  Exercise  109.  The  classes  in  botany  and  agriculture 
may  very  well  cooperate  on  this  experiment. 

Directions  for  work.  Select  several  of  the  heaviest  ears  from 
those  studied  in  the  preceding  exercise  and  several  of  the 
lightest.  Preserve  all  the  data  regarding  these  ears.  Assign 
to  each  ear  a  number  or  other  identification  mark.  Use  this  to 
mark  the  plantings  in  the  field  as  well  as  all  records. 

Plant  at  least  a  hundred  grains  from  each  ear,  planting  all 
the  grains  from  one  ear  in  a  row  by  themselves.  If  it  is  in- 
tended to  continue  the  experiment  in  later  years,  using  selec- 
tions from  next  year's  crop  for  seed,  the  rows  planted  with  seed 
from  the  poor  ears  should  be  located  at  least  several  rods  from 
those  planted  with  seed  from  the  best  ears.  (Why  ?)  Alternate 
rows  should  be  detasseled.  (Why?) 

When  the  crop  is  gathered  at  the  end  of  the  season,  keep 
the  product  of  each  row  separate  from  that  of  the  other  rows. 
Weigh  and  make  table  of  distribution  for  each  row,  or  for  as 
many  rows  as  possible,  similar  to  the  table  in  Exercise  109. 
Graphs  may  be  made  also.  Compare  the  record  of  each  row  with 
the  record  of  the  ear  from  which  it  was  planted  and  with  that 
of  the  whole  group  of  ears  studied  in  Exercise  109.  Has  the 
quality  of  the  crop  been  changed  by  selection  ?  Is  the  progeny 
of  the  best  ears  better  than  the  average  of  the  preceding  year? 
Is  it  as  good  in  each  case  as  the  ear  from  which  it  sprung? 
Are  any  of  the  ears  better  than  those  from  which  they  sprung  ? 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  chap,  xxiii. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  chap.  xii. 
DAVENPORT.    Domesticated  Animals  and  Plants,  chaps,  ix,  xi,  xii,  xiii, 
xvi.    Ginn  and  Company. 

[136] 


EXERCISE  111 
SOIL  FORMATION  BY  WEATHERING 

Materials.  Exposed  rock  surfaces,  as  cliffs ;  rock  and  soil  debris 
at  base  of  cliffs. 

Directions  for  work.  Examine  exposed  rock  surfaces  carefully 
to  see  whether  by  action  of  the  atmosphere,  water,  frost,  or 
otherwise,  small  particles  of  rock  are  being  loosened.  Note  also 
whether  larger  pieces  are  being  broken  off  by  the  expansion  of 
water  upon .  freezing  in  crevices. 

If  a  rock  cliff  is  being  studied,  examine  the  heap  of  soil  and 
other  debris  resting  against  the  base  of  the  cliff  in  order  to  find 
out  if  this  debris  (the  talus  slope)  is  composed  of  such  materials 
as  are  being  weathered  from  the  face  of  the  cliff. 

In  your  opinion,  based  upon  the  facts  discovered,  has  the 
rock  examined  contributed  to  the  formation  of  the  soil  in  its 
vicinity. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  436,  437. 
Textbooks  of  physiography. 


[137] 


EXERCISE  112 

TO  HOW  GREAT  AN  EXTENT  DOES  PLANT  MATERIAL 
ACCUMULATE  IN  SOILS? 

Materials.  Samples  of  soils,  including  a  clay  or  sandy  soil  of 
sterile  character,  a  black  loam,  a  muck  soil,  and  a  peaty  soil ;  sheet- 
iron  soil  pans  or  sheet-iron  frying  pans. 

Directions  for  work.  Dry  all  the  samples  of  soil  in  an  oven 
heated  to  a  point  just  above  100°  C.  for  several  days,  or  if  an 
oven  is  not  available,  spread  the  samples  out  thinly  on  pie  tins 
or  other  shallow  dishes  and  expose  to  the  air.  In  either  case, 
decide  when  the  drying  has  been  carried  to  completion  by 
weighing  from  time  to  time.  When  the  samples  no  longer  lose 
weight,  they  are  ready  for  the  experiment. 

If  the  samples  have  been  oven-dried,  all  of  the  water  will 
have  been  driven  off ;  if  air-dried,  a  certain  small  part  of  the 
water  will  remain  in  the  samples,  and  the  amount  will  not  be 
the  same  for  the  different  kinds  of  soil.  It  is  therefore  only  by 
drying  in  the  oven  that  the  soils  can  be  so  prepared  that  exact 
results  will  be  possible. 

Having  dried  the  soils,  place  a  sample  of  each  in  a  separate 
iron  pan  which  has  been  previously  weighed.  Weigh  the  pans 
with  soil  in  them  and  determine  the  net  weight  of  soil  in  each 
case.  Heat  each  pan  with  the  contained  soil  by  means  of  a 
bunsen  burner  or  blast  lamp  for  at  least  an  hour.  Note  any 
evidences  that  organic  material,  principally  plant  material,  is 
being  burned  or  driven  off. 

When  the  organic  material  appears  to  be  entirely  burned, 
allow  the  pans  to  cool  and  weigh  them  again.  Determine  the 
amount  of  loss  in  each  case  and  calculate  the  percentage  of 
organic  material  in  each  sample.  In  case  you  have  been  using 
air-dry  soils,  in  which  direction  would  your  results  be  influenced 
by  the  fact  that  the  soils  were  not  wholly  dry  at  the  beginning 
of  the  experiment?  That  is,  would  the  percentage  secured  be 
too  high  or  too  low?  If  you  did  not  heat  the  samples  long 
enough  to  complete  the  burning  of  the  organic  material,  how 
would  that  fact  affect  the  results  ? 

[138] 


EXERCISE  112  (Continued) 

So  far  as  you  are  acquainted  with  soil  types,  do  you  note 
any  correspondence  between  amount  of  organic  matter  and 
fertility  of  soil  ? 

Tabulate  your  results  below: 


Description  of  soil  No.  1. 


Description  of  soil  No.  2. 


Description  of  soil  No. 


Description  of  soil  No.  4. 


1 

o 

3 

4 

\Veifirht  of  pan                       .           .           • 

Weight  of  pan  and  soil  before  burning 

Weight  of  pan  and  soil  after  burning 

Net  weight  of  soil  before  burning    .     . 

Net  weight  of  soil  after  burning      .     . 

Loss  in  weight  by  burning      .... 

Percentage  of  organic  matter       .     .     . 

Reference 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  436,  437. 


[139] 


EXERCISE  113 
SOIL  PARTICLES 

Materials.  A  sandy  loam  ;  glass  tube  one-half  inch  in  diameter 
and  about  five  feet  long ;  set  of  sieves.  The  sieves  may  be  made  by 
tacking  wire  gauze  of  different  degrees  of  fineness  on  small  wooden 
frames. 

Directions  for  work.  1.  Soak  a  small  amount  of  the  soil  in 
water  for  several  hours,  making  a  thick  mud.  Stopper  one  end 
of  the  long  glass  tube  and  pour  in  enough  of  the  soil  to  fill  the 
tube  about  six  inches.  Add  water  until  the  tube  is  filled  with 
water  to  within  an  inch  of  the  upper  end.  Stopper  the  upper 
end  of  the  tube  and  reverse  it,  thus  bringing  the  tube  to  a 
vertical  position  with  the  soil  at  the  top.  Stand  the  tube  upright 
and  allow  it  to  remain  in  that  position  until  the  following  day. 
As  the  soil  falls  through  the  water  the  particles  will  be  assorted 
in  accordance  with  their  size  and  weight. 

Describe  the  composition  of  the  soil  with  relation  to  size  of 
particles. 

2.  Place  a  good-sized  sample  of  the  soil  in  one  of  the  soil  pans 
and  heat  over  the  flame  until  the  organic  material  is  well  burned 
out.  Pass  it  through  a  series  of  sieves  of  increasing  fineness, 
thus  separating  it  into  fractions  depending  on  size  of  particles. 
The  separate  fractions  of  the  sample  may  be  weighed  and  the 
size  of  particles  estimated  by  the  size  of  the  mesh  through 
which  they  are  able  to  pass. 

Tabulate  the  facts  regarding  the  physical  composition  of  the 
soil,  which  you  have  secured  by  the  aid  of  the  sieves. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  pp.  434,  435. 
CALDWELL  and  EIKENBERRY.    Elements  of  General  Science,  Rev.  Ed., 
chap,  xxiii. 


[140] 


EXERCISE  114 
EFFECT  OF  LACK  OF  DRAINAGE 

Materials.  Prepare  two  or  more  waterproof  plant  pots  by  soak- 
ing common  pots  in  melted  paraffin,  or  use  empty  fruit  or  vegetable 
tins.  Each  of  the  pots  should  have  a  drainage  hole  in  the  bottom, 
and  coarse  gravel  or  broken  pieces  of  flowerpots  should  be  placed 
in  the  bottom  before  filling  with  soil.  This  will  allow  very  effective 
drainage. 

Directions  for  work.  Plant  wheat,  oats,  corn,  or  other  grain 
in  both  pots.  When  the  seedlings  are  three  or  four  inches  tall, 
plug  the  drainage  opening  in  the  bottom  of  one  pot  with  a  cork 
stopper.  See  that  the  plug  fits  tightly.  Water  both  of  the  pots 
alike  and  supply  sufficient  water  from  time  to  time  for  several 
days  to  keep  the  soil  in  the  plugged  pot  continually  saturated. 
The  excess  water  will  be  able  to  escape  from  the  other  pot. 

Compare  the  seedlings  in  the  two  pots  from  time  to  time  for 
several  days,  or  until  there  is  a  very  distinct  difference  between 
them.  What  is  the  effect  of  lack  of  drainage  ?  When  satisfied 
on  the  point  mentioned  above  remove  the  plug,  thus  allowing 
the  water  to  drain  from  the  soil.  What  is  the  effect  upon 
the  seedlings?  Do  they  recover  from  the  effects  of  lack  of 
drainage  ?  Do  they  become  the  equals  of  the  seedlings  which 
have  been  grown  all  the  time  in  properly  drained  soil  ? 

If  a  larger  number  of  pots  are  prepared  and  subjected  to  the 
undrained  conditions,  it  will  be  possible  to  unplug  one  on  each 
of  several  successive  days  and  thus  determine  approximately 
how  long  the  seedlings  may  remain  in  saturated  soil  and  yet 
be  able  to  recover  when  conditions  are  corrected. 

References 

BERGEN  and  CALDWELL.   Practical  Botany,  pp.  437-441. 
BERGEN  and  CALDWELL.   Introduction  to  Botany,  pp.  321-323. 
WATERS.   Essentials  of  Agriculture,  pp.  122-126.  Ginn  and  Company. 


[141] 


EXERCISE  115 
STUDY  OF  A  COMMON  WEED 

Materials.  Any  of  the  common  weeds  of  the  vicinity.  These 
should  be  studied  principally  in  the  field. 

Directions  for  work.  Examine  a  weed  with  the  object  of 
determining  what  characteristics  of  the  plant  enable  it  to  be 
a  weed. 

1.  Ability  to  maintain  itself  where  present,  especially  if  a 
perennial  plant :  such  qualifications  as  deep,  tough  root  system ; 
underground  stems ;  tolerance  of  shade,  drought,  excessive  water, 
and  dust ;  ability  to  grow  in  poor  soil ;  rapid  growth ;  disagree- 
able taste,  prickles,  etc. 

2.  Ability  to  reach  and  take  possession  of  new  locations : 
such  qualifications  as  excellent  means  of  seed  dispersal ;  persist- 
ent seeds,  not  easily  injured ;    rapid-growing   seedlings ;   early 
germination ;  spreading  rhizomes. 

3.  Character  of  injury  done :  competition  with  crops  by  shad- 
ing ;   removal  of  moisture  needed  for  crops,  especially  in  arid 
regions ;  parasitism  on  crop  plants ;  acting  as  host  for  insects 
or  fungi  injurious  to  crops,  or  harboring  such  insects  or  fungi ; 
poisonous  effects  on  domestic  animals ;  other  injuries  to  animals 
or  animal  products;  other  important  facts  characteristic  of  the 
weed  studied. 

4.  Means  of  eradication  and  prevention. 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  chap.  xxv. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  chap.  xx. 


[142] 


EXERCISE  116 
IDENTIFICATION  OF  COMMON  WEEDS 

Materials.  Common  weeds  collected  from  fields  in  the  vicinity. 
Keep  a  record  of  the  kind  of  crop  with  which  each  weed  was  found 
associated.  Collect  particularly  weeds  whose  names  are  not  known 
to  you. 

Directions  for  work.  If  the  weeds  are  in  flower,  proceed  to 
identify  them  with  the  aid  of  Gray's  "  Manual "  or  such  other 
flora  as  may  be  applicable  to  your  region.  If  not  in  flower,  it 
is  possible  to  identify  only  by  the  aid  of  illustrated  floras  and 
"  weed  books."  (See  list  below.) 

Keep  notes  on  each  specimen  studied.  These  notes  should 
show  the  name  of  the  weed,  the  principal  characteristics  by 
which  it  may  be  recognized,  the  crops  which  it  commonly 
infests,  the  character  of  the  damage  done,  and  the  means  of 
combating. 

The  value  of  the  notes  for  future  reference  will  be  greatly 
increased  if  a  specimen  of  each  kind  of  weed  is  pressed  and 
mounted  on  a  herbarium  sheet  with  name  attached. 

Books  for  Identification 

CHESTNUT.    "Thirty.  Poisonous  Plants,"  Farmers*  Bulletin  No.  86, 

U.  S.  Dept.  Agr. 
DEWEY.    "  Weeds  ;  and  how  to  kill  them,"  Farmers'  Bulletin  No.  28, 

U.  S.  Dept.  Agr. 
"Farm  Weeds  of  Canada,"  Government  Printing  Bureau,  Ottawa, 

Canada. 

GEORGIA.    Manual  of  Weeds.    The  Macmillan  Company. 
MARSH.    **  Larkspur,  or  *  Poison  Weed,'  "   Farmers'  Bulletin  No.  531, 

U.  S.  Dept.  Agr. 
MARSH.   "  Principal  Poisonous  Plants  of  the  Western  Stock  Ranges," 

Bureau  of  Plant  Industry,  U.  S.  Dept.  Agr. 
NORTON.    "  Maryland  Weeds,"  Bulletin  No.  155,  Md.  Agr.  Exp.  Sta. 


[143] 


EXERCISE  117 
PURITY  OF  FARM  SEEDS 

Materials.  Samples  of  any  of  the  smaller  seeds,  such  as  the 
grasses,  clover,  wheat,  and  oats.  Seeds  from  local  dealers,  or  from 
the  homes  of  the  pupils,  preferred. 

Directions  for  work.  Weigh  out  a  sample  of  the  kind  of  seed 
to  be  tested  sufficient  to  contain  several  hundred  seeds.  Spread 
them  out  .on  the  table  and  with  the  aid  of  a  hand  lens  and  a 
needle  sort  the  kinds  of  seeds  found,  putting  the  perfect  seeds 
of  the  sort  which  the  sample  is  supposed  to  represent  in  one 
pile,  the  broken  and  imperfect  seeds  in  another,  bits  of  earth, 
chaff,  etc.  in  another,  and  each  kind  of  weed  seeds  or  unknown 
seeds  in  a  pile  by  itself.  Count  the  seeds  of  each  sort  of  weed, 
if  not  too  numerous,  and  calculate  the  number  of  each  kind  of 
weed  seeds  per  bushel,  based  upon  the  weight  of  the  original 
sample  and  the  weight  of  a  bushel  of  the  kind  of  seeds  examined. 
If  the  usual  amount  of  seed  per  acre  were  sown  from  the  lot 
sampled,  how  many  weed  seeds  per  acre  would  be  sown  ? 

Weigh  the  weed  seeds  and  the  dirt  which  was  sorted  out 
and  calculate  the  percentage  of  the  sample  which  is  not  seed 
of  the  variety  desired. 

Means  for  Identification 

BEAL.    "  Seeds  of  Michigan  Weeds,"  Bulletin  No.  260,  Mich.  Agr. 

Ex.p.  Sta. 

NORTON.    "  Maryland  Weeds,"  Bulletin  No.  155,  Md.  Agr.  Exp.  Sta. 
A  named  collection  of  seeds  in  glass  vials. 


[144] 


EXERCISE  118 

COMPETITION  BETWEEN  PLANTS 
Materials.    A  patch  of  weeds  in  early  spring. 

Directions  for  work.  1.  Locate  a  place  where  the  weeds  are 
coming  up  thickly.  Mark  off  a  space  about  a  foot  square. 
Count  the  number  of  weed  seedlings.  If  there  are  any  remains 
of  last  year's  weeds,  estimate  the  number  of  weeds  that  were 
able  to  reach  maturity  on  the  same  area  last  year.  How  do  the 
two  numbers  compare  ?  If  possible,  follow  the  area  during  the 
season  and  learn  just  what  becomes  of  the  plants  you  find  there 
now. 

2.  Allow  the  weeds  to  grow  undisturbed  along  with  the  crop 
in  a  small  part  of  a  garden.  What  is  the  effect  on  the  crop  in 
comparison  with  the  similar  crop  in  parts  of  the  garden  that  are 
cultivated?  Can  you  discover  by  what  means  the  weeds  harm 
the  crop  in  this  particular  instance  ? 

References 

BERGEN  and  CALDWELL.    Practical  Botany,  chap.  xxv. 
BERGEN  and  CALDWELL.    Introduction  to  Botany,  chap.  xx. 
BERGEN  and  DAVIS.    Principles  of  Botany,  pp.  447-453.    Ginn  and 

Company. 

CALDWELL  and  EIKENBERRY.   Elements  of  General  Science,  Rev.  Ed., 
chap,  xxxii.    Ginn  and  Company. 


[145] 


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